I agree with yor solution, but in my opinion S 3 laptimes was correct.
If you look at Z 06's corner and straight speed, you'll realize the problem is the driver.
It's no a new situation, sometimes the tester has no familiarity with car and circuit, so the laptimes are unusefull.
Top Auto, an italian magazine, published a test of 911 turbo and gt 3 in the same nurburgring configuration of Z06 test.
So i can compare the different corner and straight speed and i can realize that Corvette is very far to limit.
The driver wasn't very good.
GT 3 and turbo run with a DTM driver and laptimes is what you expect from that cars.
1:41.5 GT 3
Excuse for my english, i'm italian