PSB in Xi'an are insisting on authenticated documents even for RP renewal.

The lesson here is: do not believe what your current FAO department tells you about new visa regulations. They think they know or they don't know and they never say "I don't know". This month MANY renewing FTs are discovering the actual level of compliance to regulations that their provincial PSBs are requiring is substantively different than what they were told by their FAO. In the future, I recommend that you bring a bilingual student with you to the Immigration department and ask the officers there yourself PRIOR to renewing your visa. Of course, it is too late for that this year.
If you are working with a recruiter or a private school: if their lips are moving, they are lying. Since you are probably not legally employed now, it doesn't really matter about the changes in visa regulations.