You seem to be missing the point. There may be a Z06/track combo out there good for a stock 12.6 run, but I've yet to see it. At my local track (Sears Point) stock Z06s run 12.9 - 13.1. Stock Vipers run 12.4 at the same track. I've seen modified Z06s (intake/headers/exhaust/ecu) run 12.4 at Sears, and I've run 12.06 with the same level of mods in my RT.
Regarding whether the driver is "good" or not, check his short times compared with yours. At Sears, both I and the "good" Z06 drivers run 2.05-2.10 sec 60's, while the less experienced drivers run 2.1-2.25 secs.