Hi, made an account because I don't speedrun but I love watching them and wanted to share this clip in case it helps.

I was doing the quest to save the hornist in the band from the pit he fell in. After leaving the cutscene I immediately steped onto a rock and started sliding horizontally in a straight line. The slip starts after I fumbled around trying to get my switch to capture it so sorry for the poor quality:

I was climbing on a wall when the hornist's cart was leaving the whole and triggered the scene change. That's all I can think of that would have caused this to happen. Otherwise I have no idea how to reproduce this.

I tried to take another clip (but forgot to hit record) where I was able to attack and do some other things before grabbing a wall and ending the glitched state.

The sliding is very slow but I could see this being potentially helpful. I'm running the most recent patch on a physical cart. Let me know if you want any other info.