What do you think is the percentage of gifted kids who tolerate boredom v those that don't?

I had an interesting talk yesterday with a child psychologist specializing in ADHD who said that kids have different tolerance levels for boredom. She said that not handling boredom was a sign of ADHD and a sign of immaturity. She then said that it was this immaturity that made early ADHD diagnosis shaky because many kids just grow up and out of their inability to tolerate boredom.

Thoughts?