If memory serves right Arceus was actually kind of similar about its own player character too.
The Galaxy Expedition Team, especially the Survey Corps which you join, didn't make it very far before the player was isekai'd into the region, and your comrades comment on how far they've genuinely come in their progress in studying the Hisui region and its Pokemon once you entered the picture.
Both because of your exceptional catching ability (something that's even commented on in Arceus iirc) and because of your ability to forge bonds with your own Pokemon. Something Rei/Akari (the one you don't pick) points out because they still couldn't really become a team with their Pikachu.
So Z-A in that regard is kind of reiterating on that idea. In general, it's implied throughout the series that the player character is exceptional and one of a kind, but both Legends games were rather explicit about it in similar ways.