In single biome worlds, the terrain doesn't always match the biome (oceans can generate in plains and vice-versa)

The bug

Single biome worlds might be generating incorrectly. For example, large fake oceans can generate in the middle of a tall birch hill single biome world (MC-237636), and frozen oceans contain large landmasses. This is intended for normal worlds as biomes are now independent from terrain generation, but it is still very weird to see in single biome worlds.

Expected result

Single biome worlds should generate similarly to 1.17.1.