Or it could mean Magnus Carlsen was excepcionally endowed with the traits that make great chess players, as Phelps is to swimming. And his 29 year old self, given the same discipline he must have applied pre-19, would be a much better chess player than himself 10 years back.
I don't understand why people, including the author, are completely disregarding experience here. I agree with the author's points that a young person, even a teen, could bring a lot to the table and has his own qualities, one of which is not great experience. But that doesn't disqualify him for any job, given a hunger to learn and a passion for his work. But to suggest that "the only difference is in music taste"--well, if you measure any one young person against any one older one, you could get that result, but I'd be hard pressed to expect the same when comparing you with yourself 10 years down.