If you start playing chess too late in your life, it doesn't matter what innate talents you have, you're never going to be very good.
Picking out the effects of nature vs nurture in a random chess playing kid is not easy, and I wouldn't be so quick to attribute to innate talent that which could be explained by environment.
What is clear, however, and something which you did not seem to deny in your own response, is that playing a lot of chess when you're young is critical to overall chess performance. Without that even "intelligent" and very capable adults who started playing too late are just not going to catch up to capable kids who played a lot of chess early.
Also, I have no confidence in a 10,000 hour (or any other fixed number of hours) figure. The hours it takes to attain a certain skill in chess will vary from person to person, depending on all sorts of intrinsic and extrinsic factors, including their training regimen, the skill of their teachers, and many of the factors I listed in my earlier post.