I can't really see what bluff he could show up here with. Maybe 98s 3combos, or something like that, but that seems unlikely.

You blocking As is kinda neutral to me. Yea you block a lot of his flushes, but you block his best bluffcombos like AsJx as well... Probably it's still better to have As because you block AsKx which now can push for value.

He can have KK-QQ,77, about 6 combo flushes, and maybe KQ sometimes for value.
He would need about 6combo bluffs, and I feel like he's going to be underbluffing, so I would fold.

I'm not at 100nl yet but I'd like to post my thoughts.

We likely have all combos of AsXs, KsJs, a bunch of suited connectors that flopped a flush, and of course all the sets including QQ in our range. We also have a bunch of AK combos in our range for getting to this river - at least the ones that include one or more spades.
AQ, QJs and QTs are now part of the bottom of my range on this river, and so I think it is a fold pretty much regardless of villain's bluffing frequency otr.

I expect villain's going to show up with KK, AK, KQ or flushes such as KJs, KTs, JTs, T9s a lot more frequently then busted draws or other 3barrel bluffs which would make very little sense. For that to happen he'd have to 3barrel hands such as Ax without blocker, JJ-88, AJo or QJs-QTs, and from my experience most players don't do that very often.