I turned off clouds in a custom super flat created in 20w21a loaded up in 20w22a. 

Instead of the clouds disappearing they started moving in relation to my field of view.

The could act normally in almost every way, intersecting blocks and entities just as they should, but do so not as slowly drifting objects in the sky, but instead following my FOV around, like your hot bar or fist normally does when you turn camera. 

Leaving the world and loading it back up does not fix the issue. You have to close the whole game and boot it back up to fix this.

(sorry if this is a bit confusing. I don't quite know how to explain this well or what info would be relevant to fixing this.)