I think even if there was a first conversation, as recounted, and then the recorded call (and that combination has Z and TM in visual contact for longer than the recorded call), the ultimate conclusion doesn't change, because the ultimate conclusion is driven 100% by the confrontation that ended in a shooting.
BUT, if Serino is fabricating a first encounter, and alleging a race-based bias ("profiling") "between the lines," then he has an agenda of his own, and he is willing to be dishonest to advance it.
He could also be an insider feeding crap to ABC.
Well, the police would have a more complete timeline than we do - including store video - which could preclude the possibility of an earlier encounter. I still don’t know how much stock I’d put in an account of an account of an account, though, you know?