Whether intentional or not, I think the "deliberate practice" rebuttal is a bit of a "no true scotsman" dodge. Anyone who says they practiced a lot can be interrogated about how methodical their practice was, to see if it counts. The only way, then, to falsify Ericsson's hypothesis is to spend lot of energy on highly methodical practice over a long period of time even though you are not improving very much. Who would spend the time to do that, just to rebut Ericsson?

Ericsson's original paper says: "In this article we propose a theoretical framework that explains expert performance in terms of acquired characteristics resulting from extended deliberate practice and that limits the role of innate (inherited) characteristics to general levels of activity and emotionality." They want to claim that the only innate talent that matters is that you are active and emotional, and not that you have any innate talent for music. This paper shows that the amount of time spent practicing appears to have no effect at all on some of these basic musical skills. It shows the presence of innate musical talent, something Ericsson wants to deny.

Some people really like to believe the 10,000 hour rule. I have no desire to talk someone out of believing it if they find it motivational. But as a musician, it's obvious to me that inborn talent is absolutely necessary for high-level performance. The idea that anybody can be Joshua Bell if they just put in the time is a wishful fantasy, not reality.

This kind of "blank slatism" is popular because it satisfies our desire for the world to be fair and just. We want to believe that we can create a perfectly fair playing field where success comes from effort alone. This is a noble idea, but the danger is when we discount evidence to the contrary -- evidence that sometimes people really are different, possibly having different talents or desires. Because then we look for who to blame when things don't end up the way we thought they should.