YEAH FOR REAL, they both would have been... much worse off if not for the other, I think. Naki, because Naki, and Henry because their friendship really helped to solidify his opinion on the Pokémon world in general? Henry was never super attached to his home world, only the people he knew there -- but he might still feel homesick. Of course no amount of cross-canon CR is ever going to make him stop missing them entirely, but Naki (and by extension everything else) is kind of his... reason for staying, now, I guess. As weird as that sounds.

At the very least, he'll ask Naki to come with him if he ever decides to wander off into the wilderness for two years and not come out.