And so it starts... 340 build

You have rod bearings and a main nearest that piston with the rings broke... I'd say it's safe to assume, detonation played in that, butted or not....
Key words high lighted. Not that I'd disagree but...

though people sometimes break them when removing the piston via hammer and driver to the backside and out the deck passing by the cylinder ridge.
true, no ridge.
You can put a twist in them upon installation..that's always a good way screw the pooch, make sure not to do that
Ahhhh, yea, think I got this, but it is a good mention anyway.