Biomes of chunks loaded in 1.16.1 change to different biomes when updating. Blocks are still there, but biome behavior changes to the "new" biome.

Yeah, nothing we can do about this. This will occur with any biome mod.
Make sure you're on the latest forge & try installing chocolate fix and then trying, but there is nothing we can really do to help.
Worldgen was heavily refactored in 1.16.2 and can cause a lot of issues when trying to move worlds over.