2 - some people are order of magnitude more talented better than others at some things. Maths or music come to mind. My personal experience: it took me years of hard working to get decent rhythmic abilities. On the other hand, my sister (who is a professional musician) had a innate sense of rhythm. She doesn't even understand how that could be an issue.
Maybe it's more accurate to say that after 10000 hours, one can get close to its full potential, which varies tremendously among people.