Summary:
Clouds are at Y=192 in non-experimental worlds. According to the 1.17.40.20 Beta changelog, clouds should only be at Y=192 in experimental worlds.

Steps to Reproduce:

1. Create a new world with the Caves and Cliffs toggle disabled
2. Enable coordinates
3. Fly up to the clouds
4. Note the Y level

Observed Results:
Clouds are at Y=192.

Expected Results:
Clouds should be at Y=128.

Screenshot: