Does that mean that a Chinese citizen can register their account in the US or buy a US account and avoid having their data handed to the Chinese government?
I personally think it's a bit more complicated than that.
Yes, a Chinese citizen can register an US or any other country’s account to avoid using GCBD data center. In fact, before Apple transferred all Chinese iCloud account data to GCBD, it sent out emails to warn related users, and instructed them to change regions if they don’t want to store personal data in China.
Although register an account is easy, maintain such account is a pain. First, not all Chinese citizen can get an international credit card that support US dollars, so no way to purchase apps; second, for those who can get one, App Store may not allow to use it because it’s not a valid US card; third, even they can use that card for purchasing apps, US App Store, iTunes Store may not have those Chinese specific apps or music; last not to mention that the behavior of an US account using non US card outside US for a really lone time may trigger anti fraud protection.
I personally think it's a bit more complicated than that.