It was mentioned there was a Wicked Witch Of the South.
It was North. As in Mombi. But in the books, there was indeed a WWS, before Glinda came along, so Hilda could be her.
Oz, while you have to use a portal or a cyclone to get to it, is part of the original Enchanted Forest realm.
While it IS part of the same universe, it is not in the same realm, as evidenced by its door in the Realm Jumper.
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