I think the article itself mixes these concepts. It starts with the world-class level example, and then jumps into learning new skills over a week.

In order to be great, indeed, you don't need to be obsessed, and very rarely you cannot achieve it -- you just need to be relatively consistent. And I 100% agree that if you start early, maintaining a skill on the "better than vast majority" level is not too hard (the hard work was done in the past).

But to achieve truly outstanding results, you definitely need to dedicate tons of time and ideally be obsessed with it (at least very-very interested).