1) That's a bit strange. You may want to contact IRCC for this. I think both of them need PCC
2) You need to explain to IRCC that you do not have Hukou because your parents were born and lived in Hong Kong. Whoever handled the case may not know the difference and was just requesting document listed for applicants from "China". You can submit a letter of explination. If you have other relationship proof, you can submit that too. Back then, I only submitted my husband's birth certificate and we also provided affiliate and name changed documents because both of them changed their names since my husband was born. (that was for my MIL's application)
3) Double check your IMM 0008 etc and make sure the addresses are correct. You may be able to update/correct their addresses using web form. (I don't know the detail steps)
Good luck.
Thank you very much!
I have posted a web form asking about my situation. I did clarify that their address should be the one in HK.
Appreciate your help!