"practice accounted for just a 12% difference in performance in various domains" is not contrary to "10,000 hours of deliberate practice are needed to become world-class in any field".
For example, A) 10,000 hours of deliberate practice are needed to become a professional chess player, B) practice accounted for just a 12% difference in performance in professional chess. A and B can both be true at the same time.
And yet, (A) is simply not true, see the other mentioned study of chess players in the fulltext, a previous study involving Hambrick which found many top players falling short of 10k and many inferior players exceeding 10k, for a net explained variance of not-that-much.
I believe that Gladwell was merely suggesting that talent is not innate and the difference is somebody's ability was due to the amount of time they put into it.
The top players might have spent several hours on a related field, like what futsal is for football.
> I believe that Gladwell was merely suggesting that talent is not innate and the difference is somebody's ability was due to the amount of time they put into it.
Neither is true. Everything is heritable, as the behavioral geneticists like to say, and increasingly the genetics are being defined and nailed down; and the latter is completely refuted by the OP study and the previous Hambrick study - time spent on a field has only a weak relation with results.
> The top players might have spent several hours on a related field, like what futsal is for football.
Chess players study chess. There is no related field from which meaningful transfer will happen - at the top levels of chess, the problems are only about chess.
"practice accounted for just a 12% difference in performance in various domains" is not contrary to "10,000 hours of deliberate practice are needed to become world-class in any field".
For example, A) 10,000 hours of deliberate practice are needed to become a professional chess player, B) practice accounted for just a 12% difference in performance in professional chess. A and B can both be true at the same time.