Well even with that said, I don't think the battle is canon. I think it's just foreshadowing an enemy in KH3 or KH3D, but I don't think the fight would be canon. For example, LS was canon to the story but his fight with Sora wasn't.
That's what I'm thinking. It's not really canon, but it is foreshadowing either an enemy in one of those two games or the new villain. Then again, maybe it is MX's and Eraqus' master's nobody. Maybe, he found a way out of the Dark Realm. Then again, isn't LoD an inbetween realm? What if heartless and nobodies do exist outside the dark realm, in the inbetween realms? What if it's possible for people who've managed to get trapped in the dark realm and lose their hearts to the heartless to spawn nobodies in inbetween realms?