Basically the walls of 4-4 are kinda wack and is not that hard to clip inside of them once you know what you are looking for but the weird thing is what happens once you trigger it.

You can not longer take any damage from enemies and the walls of the levels are changed based on where you decided to clip (like you were on a different plane of existence??) and you can get stuck quite easily but the setup showed on the video could be a potential faster way to get to the end if optimized or even finding a better route.

I can get more footage if needed, I didn´t manage to clip with the pterodactyl, that one seems to work different vs walls but I wouldn´t count him out yet, you can get inside by getting hit too but that doesn`t seems good for speedruns.

No idea if it is know, I asked around and got suggested to post here to share, sorry if people know about this already.