>>52542183Imagination theory comes from two main sources. The first is Arven's post-game dialogue questioning the time travel story. Arven muses that the book and paradox pokemon existed 200 years ago, long before the time machine began bringing paradox pokemon to the present. This is seen as deliberate foreshadowing, as Game Freak is directly suggesting there may be more to the story than we know through Arven.
The second is the datamine, which confirms that an Ancient Suicune and Future Virizion are coming as DLC, complete with the signature moves Hydro Steam and Psychic Blade. These paradox do appear in the book, but are directly stated to be imaginary creations by one of the expedition members.
Pictured here:
>>52541926>>52541283These are confirmed imaginary pokemon that will become real.
That establishes imagination theory, so with that in mind anons have looked back on other inconsistencies in the story like other expeditions failing to find the paradox mons.