I think this is a better article than most of the commenters here imply. I think Adams realizes that genetics plays a role, that there is such a thing as good and bad practice. But he's not claiming any universals: rather he's proposing a deft experiment to show how ability correlates to practice rather than to innate talent with regard to one particular arbitrary skill.

I don't know exactly how his experiment would turn out. And it would be hard to decorrelate practice time from innate ability --- I certainly find it difficult to keep dedicating time toward activities in which I see no progress being made. But it's a good experiment, and a style of reality-based learning we should encourage.

My intuition is that he's right, and that the winners would be dominated by those who spent the most time practicing. But I'd love to have real numbers against which to test that intuition.