即使不是婚姻所在地的公證機關做的?

This is not what I meant. xiaobaitu has given u insight on where it should be notarized. Notary in China may have their standard in what to be notarized and what cannot. Like the law in China, it's always there, Enforeable? depends

Notary is authorized to notarize anything within their power even if the documents are issued by another state. This is the case in the US.

In China, notary may operate differently. If u want to try 出生地(縣級市,同省)辦 ur divorce certificate issued by another city, could always TRY it, but not sure w/ u could get it.

熟人helps u get the notarized docu w/o u or ex being there? highly possible. saw docu being done this way.

As long as it's notarized in China, USCIS generally may not scrutinize to details such as where the docu was notarized and who notarized it since they are all government issued documents. Substance over form. It's the content of the notarized document important, not the form.