the cross drilled wholes are to exhaust the brake pad gas between the pad and the rotor, so the pad has better contact with the rotor. And if its not vented then the brake pad gas doesnt have any where to go anyways.
either way it looks cool.
Im probibly going to do it on my bike too.
You answered your own question?
They don't need to be vented, like a slot would do, the holes simply store the gas until the rotor turns past the pads, then the gas escapes. Debris and water as well.
They also make it lighter which goes to unsprung weight.
THen there's that coolness issue too.