Is the Defintion of "Original Fiction" Not What I Think it is?

Original Fictions don't include Fan Fictions...right?

Because I always see Fan Fictions when I'm searching the Original Fiction genre, and I'm sick of seeing them. And I'm not sure if it's because people think that their story is original when it really isn't, or if they just check ever genre box so that their story is put in every category here.

When the main characters of a story include a celebrity, that's automatically a Fan Fiction, or so I've thought. And to me that means that that story is no longer an Original Fiction

So am I wrong to be irritated? Or is my knowledge of genres just all screwed up?