>asserting that the key to achieving true expertise in any skill is simply a matter of practicing.

It's been a while since I read it, but my takeaway was that the depth of familiarity brought about by 10k hours of practice in an area was just one factor of many that contributed to success. You need all those other factors in addition to the 10k hours.

I think it's just humans with our predictable penchant for distilling accurate nuance down to adjacent-but-inaccurate bullet points that created the idea that 10k hours is all it takes.