Not just biome_1 structures can generate in wrong biomes, all structures that can be put in the preset can generate in any biomes which is not an intended behavior. As I showcased in: MC-181533
This is amazing! I'll be keeping this snapshot just because of this bug 😃
To simply put it, all structures that can be generated will generate no matter the biome they are in. Including the following presettable structures: Fortresses, Endcities, Bastions, villages, and probably all other structures.
Except for Ocean monuments, when ocean monument is in a preset it doesn't let me click the new world button.
(It's pretty fun tbh. I'll definitely be playing some extra special super flat survival maps thanks to this.)