Custom entities with "minecraft:spawns_underwater": {}, component still spawn on land

Custom entities with "minecraft:spawns_underwater": {}, component still spawn on land. I have created a new fish mob, and set the biome filter to plains. It has everything else set up exactly like vanilla salmon, yet when loaded into the game, it spawn on land in the plains biome. The  "minecraft:spawns_underwater": {}, seams to be ignored and just spawns the fish on the surface of the land.