To be honest, I don't see a bug here at all.
When 'fields displayed': 'below artwork' is checked, it seems quite logical to me that that means at least one entry should be there, and if the user leaves that empty, MusicBee defaults to standard 'Album'.
psychoadepts suggestion seems perfect to me, and came into my mind as well: get creative, and use a custom or virtual tag.
Else you could post a wishlist request for a 'don't show anything at all under artwork' button, but I think there are more important things to be accomplished.
When nobody objects, I will move this to 'General' soon.