I'm not surprised by the results. Sure, the McLaren is faster from traffic light to traffic light, but the Chevy would arrive to the destination quicker. This is because the Chevy's chassis, tires, advanced and Italian-influenced Brembo brake system and aero requires little to no stopping before exiting the freeway.
20 to 30 years ago, both of these cars would not be on extreme ends, but rather in the middle — just like with the Dodge Viper (in the Z06 and ZR1's case) and the Ford GT (in the McLaren cars' case).
In fact, before 2005, an equivalent 570S would not be any faster than an equivalent C7 Z06. It would have took the equivalent 720S to only barely beat the Z06.