Fan probably knows the answer better than anybody since he played in China until he was 28 and played several years in UK afterwards. Kids at 15-17 years are middle school-er in soccer terms. Adult players are graduates of universities. If soccer player's development were to compared to general education development, Fan is pointing out up until middle school China is successful in developing young player compared to top leagues.
I think this statement is accurate to a large extent, if not considering the fishy business in China's youth soccer system. Indeed China could truly compete at a pretty high level in world youth games prior to 19 years of age.
This shows Chinese young players are just as talented as others. Innate physical deficiency was often cited as the reason for China's soccer failure in the past. Another popular excuse is that Chinese players are simply not smart enough to play highly coordinated team sports like soccer. Fingers are often pointed at the youth development in China's soccer system.
Chinese are crazy about soccer. Lots money have been invested in soccer. Maybe it's time to look at a deeper level what is really wrong with China's soccer. I feel the enigama of China's soccer is akin to that of political system. Everybody knows it is not right, and yet no one can fix it.