The thing about this 10,000 hour concept is that the clock is ticking by definition for every one of those 10,000 leading to the time in years going by. Golf has a longer peaking cycle than say gymnastics. You take a young lady who is introduced to the highest levels of training from 7-8yrs old and put those 10,000 hours of training in, and if the correct body type, correct myriad of physical and psychological aspects are aligned just right, you may get a world class gymnist. But, all the practice after early 20 something years old that could possibly be put into the training, after that peak, is all down hill and won't even maintain the high performance peak that was gained in the early 10,000hrs.
Look at Vijay Singh in golf. No one reportedly puts in more training and practice time. But, even if he doubled up on his notoriously vigorous training, he can't maintain. The clock is always ticking and mitigates against the 10,000hrs. The hours can get you to a peak of your ability, but you will peak, and I believe you can verywell peak well before the first 10,000 hrs has elapsed. You may peak at 2000 hours, and this guy in the story will probably peak well within the 10,000 hours he thinks he is going to put into this, both mentally and physically.