The Z06 had overheating issues in normal road use and Motor Trend ran the Virginia Hillclimb with the CTS V numerous times with no over heating problems.
This and the Ignition review of the Z06 leave me feeling pretty certain that the car was released in a half finished state. That's literally what the Motor Trend guys said. The team developing it must have hit some internal deadline or ran out of money.
BTW that Shmee150 guy recently did some new vids in SoCal. He visited BBi, test drove someone else's modded GT4 and some other stuff. I really like his videos. He's very cheerful and upbeat and comes off sincerely rather than like a showoff.