I slightly misread those pictures on my initial look at them, but I think my point still stands, albeit with slightly different wording. Here are the images:
Arceus,
Diancie,
Hoopa,
Shaymin.
While they each show the legendary Pokemon moving from a movie screen to the game, they also show other Pokemon existing outside of the movie screen. In two of those artworks (especially the Arceus one) the other Pokemon are looking at the legendaries being transferred, as if they exist in the world.
You are saying that these artworks demonstrate that these artworks demonstrate a shared canonicity. If this is the event linking their canonicity, it also portrays that Arceus/Diancie/Hoopa/Shaymin can escape out of fictional worlds and travel to other ones (by going from movies to games), and that other Pokemon exist in this higher world that see those movies/games as fictional. Hell, in the Diancie one we see some Carbinks making the journey over as well, there seems to be a distinction drawn between these Pokemon moving between the movie and the game, and the other Pokemon watching it happen.
How do you deal with these strange implications of those artworks? Because I can deal with them by saying "No, there isn't a higher Pokemon reality that sees a lower one as fiction, and no, Arceus/Diancie/Hoopa/Shaymin can't enter that higher reality. It's just marketing material that's inconsistent with the source material." Or "It's just a visual representation of the promotion that no-one thought about the canonical implications of."
third post's the charm