Probably not, but there is something there.
If you replaced GT6 with something completely non-realistic, like say Burnout Paradise, you'd expect a different group of people to win.
I figure that there's a spectrum between the non-realistic and reality, and the group of people that are fastest changes over that spectrum. Is GT6 close enough to the reality end that the people that win out in GT6 are the same people that would win out if they did it in real cars (which is sort of the point)?
Probably.
But there's a real chance that there's one or two who would make amazing race drivers but simply couldn't detrain themselves or develop the skills fast enough to be quick in GT. All real world race drivers are not aliens in sims. They're pretty universally quick, but they don't necessarily have the outright pace that the people at the top of the Academy leaderboards have.