Minecraft: 1.15.2
Forge Version: 31.2.0
Mods Used: simplytea-1.15.2-2.2.1.jar, themidnight-0.5.9.jar

I am going to go ahead and close this given tea trees as of 1.20 are now handled by biome tags which allow full control over this issue. If you want to stop them from spawning in other dimensions, switch the biome modifier to a overworld specific tag via a datapack.

Please cross post this to their Github/other issue tracker and link it here. I'm not entirely convinced its a bad thing.

I currently add the tree to all valid forest biomes, I am not sure if there is a good way to block other dimensions without losing compatibility with biome mods.