Ok, there’s canon evidence in Pokémon that suggests people who bond with Psychic Pokémon develop some Psychic abilities so I’m not completely opoosed to it.
But there’s gonna have to be a good explanation for this.
There's also those whom have connections to ghost types.
A ghost hunter obsessed with capturing them on film and possibly possessed frequently. Followed by a shuppet perhaps.
Could just have them be late starters.
Maybe there's a promotion to join the league as a trainer for a start up reward?