Hi
Lack of Face Time Audio is due to carrier restriction. Meaning the SIM card you have in your iPhone is from of the 2 or 3 official carriers, and/or, if you bought your iPhone through one of the 2 (soon to be 3) official carriers (Unicom or China Telecom - soon to be third China Mobile).
Not any country restriction.
It is not a political thing
It is an economic thing. Carriers have been given the right to block it or not.
Face Time Video uses data. Alot of it. Face Time Audio also ofcourse uses the data port, but it is taking away international talk revenue (if used for international calls).
If you are using a non-China carrier SIM in yr iPhone, such as the person with the Korean SIM card, then it means that he purchased his iPhone through the official carrier in China and not a truely unlocked phone in the sense that most people use the term unlocked phone, or, bought it at a 3rd party store in China that actually got the iPhone from one of the official carriers.
MMS if you recall, was not on the very first iPhone. It was introduced in the 2nd model in the USA. But when the iPhone launched in many Asian markets, MMS was blocked by the carriers as they thought they wouldnt be able to handle the data traffic or some such excuse like that. It was carrier specific just like Face Time Audio is.
Thanks