In the new Minecraft snapshot 21w38a I was found some weird nether biomes generation in my gameplay, almost of nether biomes was weird, for exemple, Warped forest is just spawned the twisted vines and some Endermans, the Soul Sand Valley there was not one Soul Sand block arround just a little fossil and the Crimson Forest just spawned the Hoglins nothing more.

Note: I wasn't find any exclusives blocks of each biome and some "tree" in both biomes (Crimson & Warped Forest).