Getting back to the topic...
It is understandable why the Buddha took issue with the Brahmanical viewpoint of ‘self’ and delineated an argument against it, and of self as of issue to the Buddha’s aims of contemplative effort where one will reify the sakkāya view of ‘I am’ whether there was a Vedic theory of self or not. And so in the second case the Buddha sets up the argument against this habit of reification with conditions, to show the process of how this misapprehension occurs, even though there is no self to be found (after all one cannot not have what was not there). All this is necessary because the Buddha is referring to an actual problem of misapprehension of the khandhas, a habit intrinsic to human nature.
It is also the nature of sakkāya-diṭṭhi to back-read a self into anything, including notions of awakening potential, nothing new going on here. For Theravāda to argue against mahāyānist buddha-nature makes as little sense as how the notion has been hijacked into Theravāda by individual teachers, if it is non-issue in the canon why work with it at all?
“I say, beware of all enterprises that require new clothes, and not rather a new wearer of clothes.” – Henry David Thoreau, Walden, 1854
Secure your own mask before assisting others. – NORTHWEST AIRLINES (Pre-Flight Instruction)