There has never been any "10,000 hour rule". In his book Outliers, Malcolm Gladwell misinterpreted and oversimplified the research into learning and training.
Honestly, I never really thought that the 10,000 hour thing was that lucid to begin with. Certain things are mastered in hundreds of hours while others are "never truly mastered". When I say I learned of it, it was reading the New Yorker article and then hearing it from my favorite kind of philosopher: stoned ones.