As a few comments mention, the reason why there are abilities that prevent priority moves from happening is to "nerf" them. You, also mention "different descriptions". Basically, these abilities do the same thing as the ability or abilities with the same or similar description, but are under a different name. Like Solgaleo's Full Metal Body ability being fairly similar to Clear Body and White Smoke. Also, like Lunala's Shadow Shield ability being fairly similar to Multiscale.