Hello,
I had this problem already in the past:
The subgenres are all listed as top level genre. This is a big issue for me.
I solved this problem in the past by clearing the Style Tag, where all my subgenres are tagged.
Now I did some tagging and instead of clearing the Style Tag, I moved the content to the tag grouping, due to the issue I encountered in the past with the Style Tag and Roon.
Now I have the same issue again.
Important: I do not not use genres extracted from file tags
Thanks for your support