I don’t think we can simply assume that it is the AU Regina showing up.
Except we still have to rationalize why the EQ is there at all then. We know she is; she’s in the scene–dressed in almost the same, if not the same, outfit she wears in the pilot. The EQ shouldn’t exist at all if there are no villains–as stated in the article–unless they just mean that after the protection spell was placed on Snowing, the EQ was powerless without Rumple prodding her into the Curse.
Except THAT makes no sense either. Rumple was the one who put the protection curse on Snowing because of his long con to find Bae. So we have a few options: No Rumple (he never became the Dark One OR never lost Bae and set out on his long path) OR we have a Rumple but he never managed to convince the EQ to try the Dark Curse and she is simply an evil queen–but not one that has aged given that Snow and Charming are now about 60 and they didn’t age Lana up at all.
The AU doesn’t make sense (what we can piece together at least) unless they rewrite large portions of the universe and character interaction. Even if it’s undone by the end of the episode, this whole “no dark curse” thing requires certain facts of the Onciverse to be undone.