Transform lets the protagonist imitate a human in Pokémon Pokopia.
The player character is a Ditto, and Ditto is famous for using Transform to copy another Pokémon’s appearance. In Pokopia, that transformation is used to create a human-like form so the Ditto can take part in rebuilding the world and interacting with Pokémon.
Transform is different from Mimic. Mimic copies a move, while Transform changes the user’s form and copies the target’s appearance and characteristics. Imposter is an ability associated with Ditto, not the move used to describe this story setup.
The human appearance therefore has an in-world explanation rather than being evidence that the player controls a human trainer. The central character remains Ditto throughout the premise.