> 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.