yea..

if this is one of them "no-read" spots, i think there are probably some % of nitterballs at this stake who don't even v-bet A4 / AT, which should literally be the only non-straights/flushes (which obv are never folding) in his value range on river once he checks turn, and i doubt he's vbetting lone Ax since you can presumably still have all 2p/straights/flushes.

the only thing is, i would expect Jx to barrel turn most of the time on that turn, which i guess is an argument calling. i still think it's just a fold though.

he can bluf some % too in this spot
you might say "but LemOn we beat bluffs", true but since we aren't calling anyway as he rarely has enough %of them with the ace hitting it doesn't matter what he's folding and it just increases the ev of our play

it doesn't increase the ev if he's not folding any non-bluffs (not saying this is the case, but obviously that was the point of my post and it depends on a.) how likely he is to check turn with a J/flush draw, and b.) how likely he is to not vbet A4/AT on river).