If it stated clearly that your wife had no criminal record in CHINA rather than in SH during that period then the PCC issued in SH will suffice I think.
For Chinese applicants, the PCC could only be obtained from their Hukou(hope you understand this term as it's difficult to explain) location rather than their residence city.
One of my Chinese friends lived in SH over 10 years but she only got her PCC from her hometown (where her Hukou is) and now she has 820visa granted.
Hope it helps.