While creating a new world for 1.19.4 I discovered a huge ocean with tons of floating villages and pillager towers. Eventually realized this was somehow a single biome world that had somehow generated without having been set but completely at random. For some reason the world seed doesn't actually take you to this world but instead a proper world starting in a savanna so yea.

Initially shared on reddit because it was a cool find but since no one else can check it out via seed input I'm sharing this way. Definitely a single biome world as I've tp'd out 10k to 30k blocks out and still nothing besides plains or oceans.