I somewhat suspect the auto-play is a bug with "accessibility -> remove animations". There are quite a lot of Google-product bugs with it enabled (nearly all other apps I use are 100% fine), though most don't render things unusable (except the recent apps list, WOW wtf). Youtube has also lately been jumping straight to "Shorts [that I have uploaded, which is zero]" when I open the "You" section, despite it being the last in the list and completely empty - this too is very likely an animation-related bug.

Why it happens with remove-animations: well I'm pretty confident they don't test with it. But it's super freakin' weird. I kinda doubt it'll get fixed though, doing so will cause "engagement" to drop, and it has been happening for most of a year now.