It's just Stephen being a dumbass under Bendis, he has contradicted himself multiple times during Bendis's Avengers run surrounding if Wanda actually do magic or not.(Also even the part about "Wanda didn't earn it" is false, she had witchcraft training with Agatha, so even if Stephen doesn't count "inherent magic" like Chaos Magic, which is also dumb anyway, next he will call Thor's natural abilities not mystical/magic in nature because he didn't "earn it" through spells and shit.)
The final say is probably Dan Slott's explanation in his Mighty Avengers with his Chthon/Quicksilver arc, where Stephen's behavior can explained as "weaken Chthon's presence on our world by denying the existence of him and anything associated with him, which includes Wanda's Chaos Magic."