I have a view that categorizes by Composer, Genre, Work, and Album. I use the "Work" field to identify the composition (for example, "Sonata for Pianoforte and Violoncello in A Major, Op. 69, No. 3"). This view lets me find all the performances of a particular piece very quickly, and I'm quite happy with it. My tagging is not always consistent - for example, I might tag one performance with the genre "Sonata" and assign two genres to another - "Chamber Music;Sonata". MC has no trouble with this. All performances tagged as Sonata will appear in the list, even if Sonata is the second genre in the tag.
A remote view set up the same way doesn't work like this. I will see "Sonata" as a genre in the categorized grouping, but it only includes performances that use EXACTLY the same genre tag, which turns out to be "Chamber Music;Sonata". The performances tagged only as "Sonata" aren't listed. In other words, the grouping identified as "Sonata" is matching a compound tag "Chamber Music;Sonata" but not a simple tag "Sonata". I have experimented by adding and removing second genres and confirmed that as long as one performance is tagged with both genres then only those with both genres will be listed.
I think this may be new behavior. I'm using 29.0.47 and I would have noticed this before as I use my Composer/Work view a lot.