Very few biomes spawning in Nether

Hello! I've been playing in both 21w39a and 40a lately and in both snapshots, it seems like the only biomes that properly spawn are the nether wastes and basalt deltas; in soul sand valleys, only structures like fossils spawn, and in the crimson and warped forests, only vines spawn. I'm not sure if this is intentional, but since I can't find anyone else reporting this, I figured I should do it myself! Have a good day!