The biome generator is independent from the terrain

[GamingCrew69]

The biomes generator does not have a way of determining whether the terrain should have a mountain or a plains biome depending on the type of terrain (except for oceans). There simply is not a value that changes depending on the terrain type (except continentalness at the edges of continents and the river value near rivers) which means that the biomes are completely independent from the terrain. This means that a jagged spikes biome can spawn on a plains terrain type and a plains biome can spawn at the top of a mountain at y=300. This issue did not exist back in 1.18 where biomes were dependent on terrain type.