This response explains how the system works, and if there is a limit on sub-genres it's fine. However, it would be helpful if there was a warning, like there is with the tags, but I disagree that the sub-genre 'family saga' couldn't apply to another genre, other than Literary Fiction. However, if that's the case then we'll just have to live with it, but I think that being able to use that sub-genre with other genres might be helpful to readers when they're choosing a story. I don't believe, though, that wanting to use that sub-genre with another genre means the story has lost its focus.