[quote=@Crimson Flame]
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.
[/quote]

There's also those whom have connections to ghost types. 
A ghost hunter obsessed with capturing them on film [s]and possibly possessed  frequently[/s]. 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?