I believe you and kimngan are maybe overthinking this. 3 professional references from one of the positions you are submitting experience for - that’s it, I wouldn’t read more into this or overcomplicate things. Say you are submitting, heck, even 2 previous position experiences. You don’t need references for all of them, the “sponsors” could just be from the latter position submitted (even if it’s under 48 months). Of course, what counts is the cumulative experience submitted.