This game used to be my childhood back then! Waluigi pinball had such a nice tune, so it was nice to see this in my recommended! People still manage to break these games 😅 congrats!
im interested if this is a completely new technique, or if it was something that was known but not usable. If i understand it correctly, its about tilting the kart backwards and using a mushroom + jumping to get a lot of heigth? Im just surprised that it took 18 years of this game existing before something like that getting into a run. So i'm wondering if its harder and more complicated than it looks (im guessing it is).
ive done this a couple of times, the hop off the ground is frame perfect + you have to align yourself parallel against the wall so when you clip it you lose the minimum amount of speed while gaining enough height to pass the invisible wall
the jump is a bit precise, since it's a frame perfect R press, and the allignment is a bit tricky, but many people are getting it now and once you hit it is basically a free timesave. You should give it a try :D