I don't see production ever having had 'Winner vs Jury vs Pre-Jury' as a theme. Not only does it make no sense and is completely unmarketable (well, okay, it's marketable, but terrible marketing IMO: it's not an interesting concept, has no message or idea, and even if there is, there'd be no way to boil it down in any simple snappy way, to get the message across in advertising)... but the cast was seemingly never there: only 5 pre-jurors were asked to the finals, and there were several runners-up (do these count as jurors?). (You can't tell me that if they needed a 6th pre-juror, they wouldn't have been able to find enough, as surely anyone in their right mind would've jumped at the chance.)
Perhaps of course they intended to make it a four-way split (winners vs runners-up vs jury vs pre-jury... which is even dumber) but they essentially had the numbers to make this happen, so it seems extremely unlikely that, had they wanted to, they weren't able to pull that off... getting 5 winners *might* be tricky but I mean, they apparently cut Mike later on (which is absolutely bizarre to me, but whatever), so it would seem they had whatever room they needed to manoeuvre for whatever theme they were planning.
My guess is (after Champions vs Challengers failed, if even a thing), that they simply cast as many great players and winners as they could, while sticking to some semblance of even gender... rather than this "big mess" everyone's assuming.
(Winners have always been even gender in a returnee season (All-Stars and Heroes vs Villains both had 2 of each, and Blood vs Water had 1 of each), so maybe that's just a pattern they like to stick to?) (Or maybe Mike simply pissed them off somewhere along the line.)