Rotor resurface on a new set of rotors
Not good, and I don't believe that is GM's policy.
Ask the dealer if they have a set of Chassis Ears, and if so, did they use them, and if not, why not; they are a required tool for finding a noise.
It is a tool that has six leads that you attach at different locatios on the vehicle. The leads attach to a central box, that has headphones. Someone drives, you listen and change the channels (different leads are different channels). You narrow down exactly where the sound is coming from.
You might have to re-position the leads a few times, but the tool is fantastic to locate those weird sounds that bug the hell out of people.