I think if you type two words into the search system, it searches both. Like, typing in "Matt Tuck" would result in stories that contain the words "Matt" and/or "Tuck" So, that may explain the A7X results, since there is a Matt in the band.
I'm not even certain the search/tags system works correctly. I thought you were taking about mislabeling genres, if you were I'd be right on board, but I honestly think this one may be on Mibba and not the author. I really don't think the search/tagging system works the way it should.
could it be the age of the writers perhaps? I understand the need for wanting to be popular, but just write a good story and ta-da!! the people will gather to your stories..... no need for the genre, tag mix up.
Then I continued reading.