[dvt]

And some people will never play in the NBA no matter how many hours they free-throw. Again, I'm not sure how the situations are different.

In some (marginal) cases, you lack a necessary feature of being an expert in X. I don't see how this breaks Gladwell's position.

[jacques_chester]

Because performance is not usually a step function. It is a continuum. If it's a continuum, variance in training time to reach expertise is not surprising.