hotturnip where are you seeing the artists advertised in this manner? In the app, both artists are credited by their full names (first and last).

If you're nitpicking how they're referred to in this discussion, I think that krazykanuck is on the money, it is a function of simplicity.
Folks likely just dropped the uncommon piece of the respective full name because it is "easier". I don't think there's any malice in it (although I think some of the criticism concerning her design has been very unfair).