I love the idea of finding this secret. That being said I haven't done much testing but I'd love to. What I found odd was after you down the gatekeeper the door reopens and the jumping puzzle now spawns platforms to that mystery gate. That's odd, and completely intentional. I don't care what anyone says. If the devs put that in the game it is there for a reason. Only logical explanation is that whatever we are missing in the vault is completely inaccessible bc it was cut from the game last minute like so much other content. I can't think like that though my curiosity to explore and solve is to strong