So, how old *are* the Chinese gymnasts?`

[Mordekhuul]

Age matters becuase the IOC (iirc) has set the minimum age limit for competitors to 16. If you are under 16, you are not allowed to compete in the Olympics (win or lose). This was done to prevent very young athletes from being overworked by those who should be in charge of them, be it parents, coachs, country, etc.

So the problem isn't that the young girls won, it's a question of whether or not they are old enough to be competing in the first place.

Indeed. Argue against the rule, but the mere presence of the rule means that countries complying are at a competetive disadvantage to countries willing to break it, as well.