The dynamic registry loading code calls RegistryKeys.getPath which, unlike getTagsPath, is unpatched by Fabric API. This means that my custom bingo:difficulty dynamic registry gets loaded from data/<namespace>/difficulty instead of the namespaced data/<namespace>/bingo/difficulty.

I don't think it's new in 1.21.2, which would technically make fixing this a breaking change.

Is this a new issue in 1.21.2? Or are you seeing this in an older version as well?