I disagree that new rotors need to be cut. Maybe this is standard practice with chinese rotors that are popular now - I will not buy these - but quality rotors should be straight and balanced when you open the box.

You MUST clean the hub with an emery cloth and you MUST incrementally torque the rotor bolts in a criscross pattern. If you mount the hub and load the bearing then measure runout, the rotors are crap or they were mounted improperly.

I dont like cutting rotors at all (once they are imperfect the metal has changed) but since it's a wheel-bearing job to change them it's tempting to cut them. But it is only delaying the inevitable.