Well, as a 3x3x3, 27 is entirely understandable (though potentially unlikely, if there are any invisible enemies in that area you'd attack them so...)
I actually tend to think of at least some of these attacks being ricochets, arcs of blood from enemies, some being knocked into others, etc. It certainly seems unlikely that, say, it's a dagger point-first entering the eye of every target hit (and, I guess, maybe nicking the ear of those missed). At least some is surprise, morale, confusion, etc.
Hmm....you mean if there were flying enemies stacked on top of the ground enemies in every possible space. Yeah I guess that's possible, though potentially unlikely is a bit of an understatement. Still can't hit 36 though, it's pretty clear that Regicide's complaints are based on a some form of misunderstanding of the rules.
And yeah I agree with you on justification. If there was a tightly packed group of 9 people, you could easily injure them all without having to fire 9 actual shots.