World set to single biome type, that is set to any ocean variant still generates normal terrain with ocean variant biome tag.

I am trying to make an underwater build and I wanted to make a world that was just ocean. I set the world to single biome and set cold ocean as the biome. When I generate the world it will generate normal terrain like a regular world with the only difference being the biome tag will say the ocean biome you selected. I have attached 5 screen shots of 2 different times I have tried to create an ocean only world, yet it only generates normal terrain.