Hi, I'm G-SANtos from Brazil.
Maybe yes, maybe not. I'm more inclined to believe this scene happened during KH1, as all other scenes in the video, happened somewhere during the period from KH1 to KH2.First of all, note that Mickey has worn five outfits in the franchise: His Disney outfit, the black coat, and three KH outfits. Out of all of these, he's wearing his CoM outfit, which means before KHII, and he's wielding the Star Seeker.
If you don't see my point, read the Director's Secret Report XIII. Mickey has already been in the Realm of Darkness before, and I believe Birth by Sleep - Volume Two might tell the remaining two of the "four untold stories" and reveal some other things, like the nature of the data that DiZ hid in Sora. You can clearly see him recording data in front of a sleeping Sora. I think we'll have first the BbSv2, and then get KHIII.
Nomura stated that Sora would be a wielder regardless of Ven, as he was always chosen. The "Sora is not a true wielder" is just Braig and Xehanort's assumption.