Updating servers makes generating new chunks empty

I updated my snapshot server from 20w20b to 20w21a and it resulted in server generating empty chunks in a flat world

The server also gave 3 Errors at the start which I believe were not present in the previous snapshot:
[15:36:17] [main/ERROR]: Unknown biome, defaulting to plains
[15:36:19] [main/ERROR]: Unknown biome, defaulting to plains
[15:36:19] [main/ERROR]: No key layers in MapLike[{}]; No key structures in MapLike[{}]