Those KH movies are parts of game packages developed by SE, and you know full-well that a Disney-produced feature isn't the same thing as Square packing cutscenes and cinematics as new material from in-game assets. (Back Cover is a slightly different case, but it's also incredibly short and doesn't quite make it to an hour in length)
Moreover, Disney has no issue merchandising Kingdom Hearts -- they just can't. One of the old staff members will have to corroborate this, but SE has a larger merchandise stake in the series and Disney doesn't push for much outside of what Square makes because, again, they don't want to piss off Nomura. These projects, including Seth Kearsley's pilot, don't go very far because Nomura's approval or lack-there-of stops them dead in their tracks.
We know this happened with the animates series, we know this is why it took so long for Sora to get into Smash, and we have good reason to believe that Nomura shut down a young adult novel series about KH a few years ago. I wasn't kidding or being hyperbolic, Disney doesn't want to go against Tetsuya Nomura's wishes, even though they own the IP outright.