Reply to Quick hands eq technique?

I've had the chance to watch some bigger name DJ's from a vantage point where I can see what they are doing. I've noticed many of them doing what I can only describe as quick hands. Their hands will move quickly back and forth between the different eq knobs with 8 or more touches over the course of a second or two. Sander Van Doorn in particular did it a lot. Their hands move so fast I have a hard time seeing how they are even turning the knob when they do this, but I'd assume the changes they are making are small.

What exactly are they doing? Is it a way to modify a lot of parameters subtly at once, or is it all for show?