Version 1.20.1

Modlist:
BCLib 3.0.14
Better Nether 9.0.10
TerraBlender 3.0.1.7
Regions Unexplored (Fabric) 0.5.5+1.20.1

Warped Forest, Crimson Forest, and Soul sand valley generate as nether wastes when these mods are installed together. The betternether old warped trees and crimson glow forest trees generate fine, but vanilla warped and crimson trees as well as the entire soul sand valley don't generate.

I tested without Regions Unexplored to see if it was a terrablender issue, generation was fine. I also tested with only BcLib/BetterNether installed and generation was still fine.

Together, vanilla biomes look like this:

Crimson Forest

Soul Sand Valley

UPDATE:
I tested again with all the mods together without using the BetterX worldtype and vanilla biomes generated as they should, so it looks like BcLib is the cause.
To clarify, this isn't fixed. I was using BetterX worldtype previously, now with default world generation the vanilla biomes are spawning properly, with their BetterNether additions.

Crimson Forest

Soul Sand Valley

I would close this, since BCLib compatibility isn't your guys' priority. I'll let you do the honors though, just in case whoever reads this can fix it.

added workaround in b329899