Well a lot the Chinese in China don't want their daughters to stop basic education and leave home at 14 to become a model in Milan or Paris. This is just the way of the Chinese culture. What I find with Du Juan and Mo Wandan is that they're the same age as the top early 20s models, but they seem to be smarter, and modeling is modeling, either clothes Made in China or couture in Dior. It's the modeling skills and attitude that makes the clothes look good. Looking at Mo Wandan at Dior you couldn't tell that ravishing creature was modeling the ugliest clothes before, but she has the poise, grace, and the looks.
Also, it's been said before but it's the whole China rising Superpower consciousness that makes the fashion world to use Asian models now.