These aren’t agents sent into China, but assets in China who were arrested/killed. 18 to 20 between 2010-2012
https://www.nytimes.com/2017/05/20/world/asia/china-cia-spie...
https://www.nytimes.com/2017/05/20/world/asia/china-cia-spie...
Assets have no special training and routinely put their lives on the line anywhere in the world they live and are recruited.
In USA it tends to be Agent/Asset whereas the rest of the Anglosphere tends to use Officer/Agent.
That’s not to say their identity is always kept secret, however. They are often discovered and only expelled at a later date when a message needs to be sent.