The bug

If the player is above world height in a 32 block tall world, new terrain stops rendering. Like this:

Video showing the bug:
https://youtu.be/gqpWL0uRoYk

This bug seems to only happen on a world thats 32 blocks tall.

How to repoduce

1. Load custom world 21w08b_32_norender.json
2. Go above y=32, go into a place new terrain would generate and look horizontal
    Terrain doesn't render
3. Look down at new terrain
    Terrain renders
4. Go below y=32 
    Terrain renders