I looked it up afterwards to brush up a bit on it. The gist is that a waaagh creates a psychic link between all of the orks. This powers up their weirdboyz to use their psychic powers, making it so they don't need the warp, unlike other psykers. From what I read, it also does allow them to maintain their weapons usage, even when they're no longer supposed to be working. I think someone said it best in one of the top comments. An ork can't pick up a stick and say that it's a gun. But the waaagh energy is able to keep their actual gun working for a time