Right now you can, when browsing the full anime list, choose to hide animes you have. Can you make an option there to hide animes you don't have ?
That way when having all animes listed by genre, you can have it show all the ones you have, which can be usefull if you need a quick reference of which animes you have of that category.
Probably because you can make your own MyList. Except you can't sort them on TV, OAV and Movie. I would like that as well, but it's not really something important IMO.