Here is a possible explanation of why Ven. Bua said those things. Please note this is my own speculation and therefore not to be trusted.
Looking at the way he describes the citta, one can see that the same descriptors apply to Nibbana, e.g. deathlessness and not subject to the rules of existence: anicca/dukkha/anatta. Surely he would have known that the descriptors he was using to talk about the citta were the same as those used to describe Nibbana in the Canon; his biography
states that he passed the third level of Pali studies which I imagine must entail a thorough knowledge of the canon.
If he is indeed a Noble One and is speaking from personal experience, then I can only conclude that he is using the word citta as a synonym for Nibbana. Why he would use the word citta in this way could only be known by him but the venerable one has since passed on so we will never know.
Here is Appendix 1 from Ven. Bua's biography on Ajahn Mun, Acariya Mun: A Spiritual Biography
, formatted by myself for readability. Good food for thought.
After his biography of Ācariya Mun first appeared, Ācariya Mahā Boowa received many inquiries and much skepticism concerning certain aspects of Ācariya Mun’s life and practice. Most notably, he encountered criticism that, in principle, some episodes appear to contradict specific long-held views about the mind’s pure essence and the existential nature of the fully-enlightened Arahant. Ācariya Mahā Boowa was quick to point out that the truth of Ācariya Mun’s profound and mysterious inner knowledge lies beyond the average person’s ability to grasp with the intellect or define in a theory. In this context, he included those students of the Pāli scriptures who, believing that the written texts comprise the sum total of all aspects of Dhamma, assert that scriptural doctrine and convention are the only legitimate criteria for authenticating all of the countless experiences known to Buddhist practitioners over the ages. In order to address this issue, Ācariya Mahā Boowa included an addendum to subsequent editions of the biography. The following is a summary of his remarks:
Ācariya Mun often told his disciples how he daily experienced such an incredible variety of Dhamma within his heart that it would be impossible to enumerate all of the things that were revealed to him. He was constantly aware of things that he could never have imagined to exist. The extent of his own experiences left him in no doubt that the aspects of Dhamma that the Lord Buddha and his Arahant disciples witnessed from the moment they attained full enlightenment until the day they passed away were simply incalculable. Obviously, they must have been numerous beyond reckoning.
Ācariya Mun stated that the Dhamma inscribed in the Pāli Canon is analogous to the amount of water in a small jar; whereas the Dhamma that is not elucidated in the scriptures is comparable to the immense volume of water contained in all the great oceans. He felt it was a shame that no one thought to formally transcribe the Buddha’s teachings until many hundreds of years after his death, and the deaths of his fully-accomplished disciples. For the most part, the nature and emphasis of the Dhamma that was eventually written down was dictated by the particular attitudes and opinions of those individuals who compiled the texts. For this reason, it remains uncertain to what extent the compilations that have been passed down to us are always an entirely accurate reflection of what the Buddha actually taught.
Ācariya Mun frequently declared to his disciples: “Personally, I feel that the Dhamma which issued directly from the Buddha’s own lips, and thus emanated from his pure heart, must have been absolutely amazing because it possessed an extraordinary power to inspire large numbers of his audience to realize the paths and fruits of his teaching with apparent ease. Such genuine, living Dhamma, whether spoken by the Buddha or by one of his Arahant disciples, had the power to transform those who listened, allowing them to clearly understand his profoundest meaning in a way that went straight to the heart. As for the Tipiṭaka, we study and memorize its contents all the time. But has anyone attained Nibbāna while learning the texts, or while listening to recitations of the suttas? By saying this, I do not mean to imply that the scriptures are without benefit. But, when compared with the Dhamma that issued directly from the Buddha’s lips, it is obvious to me which had the greater value, and the greater impact.
“Consider my words carefully, those of you who believe that I am advocating some false, ignoble truth. I myself wholeheartedly believe that Dhamma coming from the Buddha’s own lips is Dhamma that forcibly uproots every type of kilesa from the hearts of his listeners – then and there on the spot, and to their total satisfaction. This is the same Dhamma that the Lord Buddha used so effectively to root out the kilesas of living beings everywhere. It was an exceptionally powerful teaching that reverberated throughout the three worlds of existence. So, I have no intention of encouraging the Buddhist faithful to become opinionated bookworms vainly chewing at pages of scripture simply because they insist on holding tenaciously to the Dhamma they have learned by rote, and thus cannot be bothered to investigate the supreme Noble Truths that are an integral part of their very own being. I fear that they will mistakenly appropriate the great wealth of the Lord Buddha as their own personal property, believing that, because they have learned his Dhamma teaching, they are therefore sufficiently wise; even though the kilesas that are piled as high as a mountain and filling their hearts have not diminished in the least.
“You should develop mindfulness to safeguard yourselves. Don’t be useless scholars learning to no good purpose and so dying in vain because you possess no Dhamma that is truly your own to take with you. It is not my intention to in any way disparage the Dhamma teachings of the Lord Buddha. By its very nature, Dhamma is always Dhamma, whether it be the Dhamma existing within the heart or external aspects of Dhamma like the Pāli scriptures. Still, the Dhamma that the Buddha delivered directly from his heart enabled large numbers of those present to attain enlightenment every time he spoke. Now contrast that living Dhamma with the Dhamma teachings transcribed in the Pāli scriptures. We can be certain that the Dhamma in the Lord Buddha’s heart was absolutely pure. But, since the Buddha’s teachings were written down only long after he and his Arahant disciples passed into total Nibbāna, who knows, it may well be that some of the transcribers’ own concepts and theories became assimilated into the texts as well, reducing the value and sacredness of those particular aspects accordingly.”
Such was the essence of Ācariya Mun’s discourse. As to the criticism that the Pāli Canon contains no evidence to support Ācariya Mun’s assertion that deceased Arahants came to discuss Dhamma with him and demonstrate their manner of attaining total Nibbāna: If we accept that the Tipiṭaka does not hold a complete monopoly on Dhamma, then surely those who practice the Buddha’s teaching correctly are entitled to know for themselves all those aspects of Dhamma that fall within the range of their own natural abilities, regardless of whether they are mentioned in the scriptures or not. Consider the Lord Buddha and his Arahant disciples, for instance. They knew and thoroughly understood Dhamma long before the Pāli Canon appeared. If these Noble individuals are truly the genuine refuge that the world believes them to be, it is clear that they achieved that exalted status at a time when there were no scriptures to define the parameters of Dhamma. On the other hand, should their achievements thereby be deemed false, then the whole body of the Pāli Canon must perforce be false as well. So please decide for yourselves whether you prefer to take the Buddha, Dhamma and Sangha as your heartfelt refuge, or whether you want to take refuge in what you chance to read and what you imagine to be true. But those who choose to be indiscriminate in what they eat should beware lest a bone get stuck in their throat...
Regardless of all this, I myself try not to cling to any
words, as per the Kalama Sutta (from accesstoinsight):
Now, Kalamas, don't go by reports, by legends, by traditions, by scripture, by logical conjecture, by inference, by analogies, by agreement through pondering views, by probability, or by the thought, 'This contemplative is our teacher.' When you know for yourselves that, 'These qualities are skillful; these qualities are blameless; these qualities are praised by the wise; these qualities, when adopted & carried out, lead to welfare & to happiness' — then you should enter & remain in them.