Oh, someone beat me to it. Here's the description from my duplicate issue MC-236657:
> Above a certain Y level, the light level of blocks darken. This Y level seems to vary based on how high the blocks are when you load the world. When I generate a world, it's usually around 175, but when I leave and reenter the world near my tower, that height increases.
Occurs in 21w37a, but it seems that you are only rotated after exiting the perspective with armor stands. While spectating them, the f3 menu actually differs from your camera rotation. Item frames still do it, furnace minecarts do not.
I believe this is the same bug as MC-26633. I did search awhile ago, just spent awhile creating the issue as I was experimenting with it.