Okay apparently wrong info--I was basing it on some autosave comments in the code, rather than actual testing, which
somehow is not doing what the code looks like it's doing
You are absolutely correct.
The original intended behavior was to wait until the player's first actual turn, so the saving that's occurring immediately after the animation was an accident that apparently happens because the logic blocking for the intro animation puts the logic in a state that allows it to autosave just before it switches over to player control.
The only reason that works at all is because the intro takes longer than it does for the regular UI animation to complete. You can confirm this effect by turning on the map intro and hitting spacebar to cancel it as soon as you enter a new floor--it
won't autosave until you take the first turn, as expected.
So the alternative here would be to just make sure it saves as soon as it can, even if the player hasn't taken a turn.
I've rewritten the autosaving to be controlled directly from the parts list animation, since that's what's holding it up--now it will save as soon as the map appears, before your first turn.