Yes drilled rotors cool faster, but it is proven that drilled/slotted rotors make noise under braking. My Camaro used to have drilled and slotted rotors all around, and it made the same noise this bike does, not a squeek, but like a vibration.
Well, I'll believe you if you can provide a link to some test, some expert, or some brake company that says this.
I had a RD 400 that came with un drilled discs. I paid to have them drilled at a machine shop. I never heard any difference.