I never said that?You don't necessarily need to be a Pokemon trainer to have a Pokemon, js.
In the E3 Demonstration, they said that Lillie isn't a Pokemon trainer.
https://youtu.be/UC-uLg_5RIA?t=1850 It's said a few seconds after 30:50.
EDIT: Speaking of Ultra Beasts... I'm curious if they'll have their own Pokedex or whatever. Like their own numbering system.