By all means please delete this or move this somewhere if it doesn't belong, but I just got a strange theory:
Game Freak seemingly did an amazing job at scrubbing this demo, so much about stats and moves were stubbed. They payed extreme attention to take them out. Yet inexplicably, "all" the pokemon's sprites and shinies were still in the files. Why would GF pay so much heed to stub spoilers, but somehow overlook the sprites? They were discovered after only a half a day or so after the demo released, even without prior datamining knowledge from ORAS, that seems a bit fishy.
The reason I put emphasis on the "all", was because of the general anonymity of the "events" in the SM demo, there's four events we have yet to discover, two of which involve the seaport, seeing off a girl heading away, and watching a shady deal. And the people at the seaport, mention far off places.
Seeing off the girl is the last event, its in November, on the 11th, a perfect week before the release of the full game. This event could lead to something interesting. What could it be? Well, Game Freak has been showing off an awful lot of pokemon haven't they?
The next bit of SM information is on the 27th, and following the previous cycle of news, there could be more on NOV 1st, and then on NOV 15th, that's 3 pieces of news, and, if you add the events in the demo that are yet to hit, that's another three, Thats a potential 6 pieces of news before the release.
"ALL" Pokemon were leaked? What if perhaps the demo has more to it than we think? What if the pokemon in data list are "supposed" to be there? Because they're "Supposed" to appear. What if the demo takes us somewhere? What if the demo shows us more "random" events. Like how Alolan Dugtrio was seen. Have any of the data miners even seen what the other planned events are going to be?
tl;dr "The pokemon discovered in the data mine are in the demo, because they're "set" to appear at later dates due to the massive amount of pokemon already shown off by Game Freak, the future date events will be how you see them."
(This theory is already a bit debunked with the Ultra beasts in the data as well, why the fuck would they show so many in a demo.)