Yeah that's youtube shorts. One of the reason I use vanced even if I have youtube premium is that it's the only way to just turn that half baked feature off. I wouldn't mind youtube's tiktok clone as much if it at least didn't have such a weird UI. It's so badly integrated to the rest of the app that it completely messes with your navigation buttons, and in general looks like a separate app inside the app. Which means performance is very bad too.

Instagram pushes its own tiktok clone very hard too (Reels), but the experience is a lot smoother compared to YT Shorts.