The pale garden is not added to the #minecraft:is_overworld biome tag. I would expect all overworld biomes to be part of that tag. A notable side-effect of this is that strongholds cannot generate in pale gardens since #minecraft:has_structure/stronghold used the #minecraft:is_overworld tag

How to reproduce

1. Enter a pale garden
2. run /locate biome #minecraft:is_overworld
3. Notice the nearest biome is some other biome nearby