[vjaswal]

Maybe it was in the Free Solo movie or other interviews, but I thought he said that his route during Free Solo was a difficulty level of about 7/10 for him. So he was comfortable enough that it was not the hardest climb for him; after a ton of practice on that route, with ropes, of course.

So to be statistical about it, the difficulty level for him was at the edge of 1 standard deviation of the mean of his capability. Maybe that's enough margin that he could detect when he's really in trouble.