Considering Bhikkhu Bodhi’s comments (see below) I understand it as follows:
Respect the elders and the seniors is a great Buddhist monks tradition and ethics.
Even a 50 year old person (even he is an Arahant) ordained today has to bow down to the person (younger and no an Arahant) ordained yesterday.
The same way if a person disrobe and re join the order, the person will lose his seniority.
I think lay person (even if the person is an Arahant) has to bow down to a monk (not Arahant) based on the same principal.
In that sense Buddha is the highest in the order.
Am I correct?
Bhikkhu Bodhi wrote:Thus the Buddha is distinguished from the arahant disciples, not
by some categorical difference in their respective attainments, but by his role: he is the first one in this historical epoch to attain liberation, and he serves as the incomparable guide in making known the way to liberation. He has skills in teaching that even the most capable of his disciples cannot match, but with regard to their world-transcending attainments, both the Buddha and the arahants are ‘buddho’, "enlightened," in that they have comprehended the truths that should be comprehended. They are both ‘nibbuto’, in that they have extinguished the defilements and thereby attained the peace of nirvâna. They are both ‘suvimutto’, fully liberated. They have fully understood the truth of suffering; they have abandoned craving, the origin of suffering; they have realized nirvâna, the cessation of suffering; and they have completed the practice of the noble eightfold path, the way leading to the cessation of suffering
“As the lamp consumes oil, the path realises Nibbana”