Let us be honest, the time test on tg is not at all realistic as a measure for results. That said, in the 'stig' book, he did suggest that Lewis was unbelievably fast whilst being unbelievably casual which would support the time he got. I doubt they let him do thousands of laps, hell, I doubt they needed to, didn't McLaren do significant amounts if testing with the mp412c at the tg track? Would have given him plenty of experience if he did some of the driving for them.
Anyway, shows he is unbelievably quick, whether he's faster than anyone else though can not be judged by the tg race
kd