I think it's totally standard, coolerville. You could raise the flop for info however outdated that is, though you do fold out the absolute crap that he's holding.

His stats would be interesting but he's took an aggressive line and I'm never folding the nut flush on a non-paired board

" or is this just me overthinking and the spot is an auto cooler??"
Auto cooler. Simply no way I am folding A high flush. Yes he may have str flush. But folding A high flush is simply -ev in the long run.

That was pretty much my thought, plus the hand is a couple months old now, so God knows what reads, if any I had, and as a zoom hand the dynamics are reduced

If we look at the big picture, if you always call there no one is going to exploit you. And that happens so rarely that it doesn't even affect your winrate in the long run. If he is bluffing/over playing 1/4 times the call is +EV. This is kind of a spot that you shouldn't focus on a lot. Whether you all or not doesn't affect the winrate, as nutflush vs. straight flush doesn't happen that often.

To be able to fold you should be pretty damn sure about his straight flush. And even the most nittiest of players tend to do brainfarts at micros.

You lose to one combo of 56hh that has somehow bet flop turn and now jams river. I would be more inclined to think they have Kxhh.