I believe the skip is a result of going through the first door without activating the fireworks. When you reach the checkpoint keep sprinting, and generally try to be fast. I believe the game is having a problem loading the level which allows you to pass through the sides of the door; which skips a mandatory fight against a mob of demons.

I wanted to confirm that this does in fact work on the Xbox Series X, which has the fastest loads out of every version of the game. You just gotta do it pretty fast, but since it works on that version, it'll work on any version of the game. Just make sure you wait a second or two after the gate for the stairs to load, otherwise you can fall inside the stairs and get stuck there until you die. And it's Act 2-3 btw, not Act 2-2 like the 7 year old title states.