I wonder what baron reps here with these sizings

A5/56/aces

Could have JJ sometimes, maybe AJ, maybe QQ-AA sometimes, some flushes. It's not like he never has value, he is obviously super good and isn't dumb enough to only have bluffs here lol

why is he playing short stack? I thought that was heresy.

Players are 65bb deep
flop is 12bb, 432 2hearts 1 diamond Antoha checks and Baron checks
432 I don't either player has a single set in their range. CO has 55-TT. Button can have A5s, 56s, although neither of these hands have to 3bet, the hands' value alone merits a call in position.
3betting 65s,a5s has its advantages of getting offsuit aces to fold, some offsuit kings and queens. What we are left with from the CO is suited broadways, KQ, pocket pairs 55-TT, big suited aces AQ,AJ,ATs, and a few suited connectors like T9s,98s,87s

Turn J of Hearts.
Players have 5x pot. Antoha only has 4 flushes: AThh,T9hh,98hh,87hh. The AK,AQ,AJ KQ KJ QJ QT JT combinations of hearts are all blocked. The AK of hearts is removed because we expect a 4bet preflop.
Baron bets 2/3 pot when called players will have 2x pot.
When antoha calls. We can see his value range as this: 4 AThh,T9hh,98hh,87hh, 21 Jx: (12 AJ 2 KJs,2 QJs,3 JTs), (36) 55-TT, His drawing range as this: (6) 3AhQ,3KhQ

River 7 check, Baron bets 2x pot, Antoha needs to be good 40% to break even on the call. Baron needs folds 66% of the time to break even on a bluff.
For value I give Baron, 16 combos AA,AKhh,AQhh,65s,a5s
For bluffs, only hands with blockers, 12 combos: 6 AhK AhQ, 6 KhQ QhK
River Range from Antoha: 4 flushes, 54 pairs, 3 sets, 6 Ace highs
If Antoha calls AJ then does he call JT, if he calls JT then does he call TT, if he calls TT then do he call 55? 55 beats the bluffs just as good as AJ, the Jack blocker is irrelevant to the value range of OTB Baron.
The AJ blocks AA,a5s while all other pairs don't. Oddly enough after AJ, 55 is the 2nd best bluff catcher blocking a5s,65s.
Stranger than that is AJ blocks 2 of the 12 bluff combos: KhAdsc, QhAdsc.
Strangest of all that means 55 is better bluffcatcher than AJ.
19/67 AJ,77,AThh,T9hh,98hh,87hh, if 55 through KJs fold then Baron's shove will yield money.
If Antoha calls 25/67 55,AJ,77,AThh,T9hh,98hh,87hh then Baron's shove will lose money.
It comes down to whether or not Antoha will call pocket 5s.
KJs blocks 2 of Baron's bluff's combos, also blocks 0 of his value combos.
55 blocks 4 of Baron's value combos, and none of his bluff combos.

OTB definitely has nut flushes