the breath absorption techniques that were both prominent during his time
Would you say more about this? What indications do you have? There is the mention of the buddhas two teachers, but that only really mentions jhana 7-8, and that they don't lead to "disenchantment, to dispassion, to cessation, to stilling, to direct knowledge, to Awakening, nor to Unbinding". There is some mystery around why Buddha had practiced 7-8 jhana, but then seems to remember 1st jhana as a child.
Might be of interest to note that Buddha stated 4 developments of concentration:http://www.accesstoinsight.org/tipitaka ... .than.html
How might these developments relate to one another, or different forms of concentration?
Here is Sujato in A History of Mindfulness. Some more good stuff in there about pre-buddhist practices, reframing:
Three discourses in the Bojjhanga-samyutta present the claims of non-Buddhist wanderers to develop Buddhist-style meditation. They say they exhort their disciples to abandon the five hindrances and to develop, in two cases, the seven enlightenment-factors,[ 216] and in a third case, the four divine abidings.  Elsewhere too the divine abidings are attributed to great sages of the past, notably the Buddha in past lives. However, although these were indeed later appropriated by the Brahmanical tradition, they are not attested in any pre-Buddhist texts. The enlightenment-factors include mindfulness and investigation of dhammas, which is equivalent to vipassana, as well as samadhi. The wanderers ask, then,what is the difference between their teaching and the Buddha's? Interestingly enough, the Buddha responds, not by referring to, say, the four noble truths, not-self, or dependent origination, but by claiming that the wanderers do not fully understand samadhi practice in all details. This is probably what the Buddha was referring to when he claimed elsewhere to have 'awakened to jhana' (jhanam abujjhi); not that he was the first to practice jhana, but that he was the first to fully comprehend both the benefits and the limitations of such experiences. (p. 98)
Might also interest you, this recent thread on Rrichard Shankman talks see videos 9-10 where he talks about inclusive/exclusive concentration, dividing along the same/similar lines as U Pandita's samatha/vipassana jhana distinction. While this explanation seems plausible to help with discrepancies between suttas and visuddhimagga, I'd like to see more evidence from the Buddhas time, or any thoughts, as to my questions above.viewtopic.php?f=43&t=16668