Custom forest biome generates without trees

I've created a few biomes, some with one custom tree per chunk, and they work as expected, two forest biomes that should have plenty of trees but generate zero, they also don't generate tall grass and berry bushes as expected. If i set 1 tree per chunk for the custom plains biome, the biome generates the trees as epected too, so i tried to duplicate that biome, rename the duplicates to forest-something and increase trees and again the trees don't generate in the forest biomes. I'm confused.

I'm using EAP 52319 for 1.16.4.