Originally before the story mode there were meant to be playable bosses in multiplayer (each with their own theme), but some time later some of these bosses were reimagined for the story mode instead.

That playlist has leftovers of what their original boss themes were meant to be.

ah i see now

So I'm assuming LetsTortureGMod was supposed to be Pride? Judging by the fact the LetsTortureGmod mansion level's filename is "sog_pride" and his dialogue before you execute him is "I AM A ♥♥♥♥♥♥♥♥♥♥♥♥♥ GOD!"

There are 7 bosses that correspond to the seven deadly sins (The Binding of Isaac or Dead Rising 3 style), so yes