no the Stig has been quoted as saying that F1 drivers take a slightly different line through the last 2 turns. that doesn't mean that Stig himself couldn't have been an F1 driver. It's entirely possible that having so many laps on the track he found a better line vs those F1 drivers.

Also it might have been Ben Collins in the past as there has been more than 1 Stig. Also it's widely known that if the Stigs identify known, by either Stig him(it)self showing his face or one of the staff telling who he is, then he will be fired. Which is why there is no more black Stig (black driving suit vs the current white suit).

However, most likely Shoemaker put the helmet and suit on for this one time. Why? well the Ferrari FXX that was driven by the Stig is Shoemakers own car. His is the only one without white racing stripes (on black) on the car.