In Explorers, Grovyle’s future is said to be “generations” in the future compared to that of the present. The protagonist is erased from time once the future is corrected and brought back.

In Sky in Special Episode 5, Grovyle’s future is made real as well of powers beyond Dialga’s comprehension. This would all be hunky dory.

Buuuuuuut.

Super Mystery Dungeon exists and has present characters like Bidoof and Wigglytuff existing in the same timeframe as Grovyle, Celebi (the shiny one), and Dusknoir. The trio should be vastly far ahead in the timeline. The only way this makes sense if the powers-that-be pulled everyone from the future backwards through time but this would be odd since none of the future Pokémon appear again in Explorers.

Aside from the theory I pulled out of thin air, there is nothing to explain this quirk in the timeline.