I have a feeling the new legendaries are using dual type moves.

Solgaleo uses it's attack against Salamance and it's normal effectiveness. Both Steel and Psychic are normal effectiveness against Salamance.

Lunala uses it's attack against Gengar and gets super effectiveness. Both Ghost and Psychic and Ghost are super effective against Gengar.

I think Nintendo chose these match ups purposely so they didn't spoil the dual type moves.