I think it has to be something beside what happened with Nova or at least there is more to that story because i think that the Blue Fairy thought she was doing the right thing for Nova then. The Blue Fairy was thinking about what she thought was best for Nova instead of what would actually make Nova happy and what was actually best for Nova who wasn’t that great of a fairy.
And i know that we saw Red wolf with Charming, but i still think there has to be more between the story of when Snow and Red left Granny at the end of Red-Handed and when Red met Snow again in the forest with the basket of food. Like someone helped Red in some way to learn to control her power.
And the fact that Maleficent had the curse does not explain how it became an apple. Or the situation in which Maleficent used it, and how it became an apple, and when Regina traded for it, and how the blind witch got it. There is a lot of story they could do in there with the curses. They may never, but i still wonder about it.