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.
Practice matters. Especially at the upper level. There are hordes of talented "strong casuals" out there.
For becoming a chess GM you need 3 things: talent, grit(deliberate practice), starting early(10-12 is okay, 18 is too late these days).
One interesting aspect of starting early AND also persistent grit is being the youngest sibling in a chess family.
For example Hikaru had a master level older brother and of course there's Judith. The youngest siblings are ridiculously competitive against older ones.
No one with a musical background will be surprised that ear training (i.e the ability to hear musical details) is only distantly related to finger training, especially if the finger training happens on an instrument with discrete pitches, like a piano.
Ear training is a separate process, and has to be practiced separately. Playing will improve it a little, but won't fully develop it.
In fact amateur keyboard players are notorious for poor pitch discrimination. Keyboards are just switches. You don't have to find the pitch while listening for intonation, as you do on instruments that don't have frets and require very precise finger or mouth control, as well as the ability to listen to the rest of an ensemble.
The "10,000 hours to expert performance" notion originated in Ericsson 1993 (http://projects.ict.usc.edu/itw/gel/EricssonDeliberatePracti...) , which defines a very specific term, "deliberate practice" -- "In contrast to play, deliberate practice is a highly structured activity, the explicit goal of which is to improve performance. Specific tasks are invented to overcome weaknesses, and performance is carefully monitored to provide cues for ways to improve it further. We claim that deliberate practice requires effort and is not inherently enjoyable." Ericsson adds more detail in the full paper.
It's not just "are you playing piano for X hours per day".
The paper in this post mentions deliberate practice in its review of the literature, but then all of a sudden and without explanation reverts to the more generic term "practice" for all of its contributions, which appears to be defined as "how many hours did you play your instrument".
Note that "play" and "practice" are explicitly disambiguated in Ericsson.
I have a hard time believing that the authors are unaware of this distinction, especially considering that they heavily reference Ericsson.