Unique biome do not generate ocean without islends anymore ?

Is this a bug or not, whene i'm creating a world with unique biome and set any of the oceans in the 1.18 pre-release 4, the world generate a ocenans with a lot of land, trees, lacs everything is here but it's suppose to be juste an ocean, right ? 

So a wanned to know if this was a bug, or an itentional new feature.

it wasent working since the new generation came but i hoped it'd get fix, but well now i cannot create a ocean world without land.