I need to double check, but I think the size of the rotor changes. I remember talk about how a 18" spare does not work anymore but I don't think it was solely due to caliper to wheel clearance without a change in rotor size.Absolutely not true that is not how friction works.
Friction area is irrelevant, you clearly do not understand physics, I have a mechanical engineering degree I know physics. Bigger pads only make for longer pad life the physical area has no relation to stopping power, all that matters is the coefficient of friction of the pad. Larger rotor do give more leverage for stopping power yes, but I don't think this kit is changing the size of the rotor just the rotor has more contact area. You do realize that if these upgraded calipers have more piston surface area then the pedal travel would actually get longer/softer. From the link to the kit from Chevy it said the rotors have 22% more surface area, are the diameter the same as stock?