Mountain generation appears to be cut in amplified

After converting 1.17.1 amplified world to 21w44a, newly generated chunks (especially mountains) seems to be "cut off". (see attachment)

 

Steps to reproduce:

1. Create an amplified world in 1.17.1 using seed -3960577850665784980
2. Save and exit the world
3. Load the world in 21w44a
4. Teleport to the location on screenshot (-70 309 3004)