Help with Geometric details

well that’s super interesting.  Curious if you know the explanation as to why having a totally different background works (although it looks like it works, it seems to go against everything I’ve learned about RC so far).  I can’t wrap my head around how this wouldn’t cause RC to just not match the images completely.  Is it because RC will discard this background info since there is no overlap and only keep the main subject since it is detecting overlap in the main subject?