GM High Tech Performance got 12.9 out of a bone stock Camaro SS. They got a C5 Z06 to dip into the 11's.
MM& FF has been able to get an 03-04 Cobra to run 12.4 when new. They got an S197 Mustang to run a 13.4. They've been able to get the fat pig GT500 to run into the low 12's stock.
I'm not sure how these two magazines get their cars to run the great numbers they do, but I look to them as the exception and not the rule.
Of course this is coming from a guy that got his stock GTO into the 12's. But then again it took me about 5 months to get the C6 running 2-3 tenths better than the GTO. Maybe there is something to the factory freak thing and these two mags get more than their fair share.