I have 30 Genres on my PC's MC; using the same library sources I have 100(!) Genres on our IdPi.
The bug appears to be this: The Genres on my PC only use the library files while the Genres on our IdPi also include files from Cloudplay playlists.
I've searched for an option to control this behavior but I haven't found one. If there is one (or one is created), I think that its default behavior should be the same as the Windows version.