Music Genres not doing what is expected.

It is that time of year when I drag out all the Christmas jingles and play them to death.

However, this has highlighted an issue with plex and the way it seems to use Genres.

All my files are tagged with the relevant genre and yet plex only seems to find specific artists who have at least one song of that genre.

So if I select the genre Christmas it lists such artists as Jethro Tull (who have 1 Christmas album), Marillion (who have one Christmas Album) etc. If I then ask Plex too randomly play the filtered Christmas music I get all the Jethro Tull and Marillion albums!

It also does not show any compilation albums - obviously most Christmas albums are compilations.

So does plex not use the track id genre to filter? If not what is the point of it?

I run both Plex and the very old Logitech Media server on my Qnap. Logitech always delivers as expected. If I filter by the genre Christmas then it plays every Christmas track that has a Christmas Genre tag and no others.

Am I missing the point of the genre filter in Plex?