See video. When I twist my in-game head, the colours move with it instead of being fixed to the screen.

In the Image, you can also see the debug screen and circled are the clouds that seem to be (just about) clipping through chunks that are whitewashed by the render fog. This is the same effect as you get when you're looking at a build that soars higher than the clouds.

I am not experiencing MC-186064.

This only works with fancy-clouds. Fast clouds are normal.