I thought that 10,000 hours was an order of magnitude estimate: that for most skills, an expert will have closer to 10,000 than 1000 or 100,000. It isn't that profound: almost no one really lives long enough to put 35 years of good effort into anything, and most people have enough time to put at least a few months of effort into something, so the log-scale average ends up being about 10000 hours.
I gave my copy of Outliers away when I got old enough to know better, but didn't even Gladwell suggest that this was more of a prerequisite than a guarantee? That is, if you haven't put at least 10,000 hours into something yet, don't expect to be an expert at it? Or broadly, don't expect to put 100 hours into something and then get disappointed that you aren't the world's best.