What happened?

When using BetterX world type with biomes o' plenty, the BoP biome surface blocks are replaced with netherrack. For example, withered abyss generates with only netherrack instead of blackstone, visceral heap is netherrack instead of flesh, and erupting inferno is netherrack instead of brimstone.

When using default world type, BoP biomes generate as intended, but the following BetterNether biomes do NOT generate: bone reefs, sulfuric bone reefs, nether grasslands, nether mushroom forest edge, old warped woods.

I tested this in both Fabric and Forge using Sinytra connector, and found the exact same behaviour in both versions. This is all for Minecraft version 1.20.1.

BetterNether

9.0.10

BCLib

3.0.14

Fabric API

0.92.6

Fabric Loader

0.16.14

Minecraft

1.20.1

Relevant log output

Other Mods

Biomes o Plenty

Not sure if this will fix it but I have not gotten an issue like this. Perhaps, can you try adding Biomes O' Plenty's nether biomes to BCLib's Biome config so that the BetterX world type knows about them? I have them spawning normally for me, at least through connector, not sure about native fabric.