Can I enjoy 72h transfer in Shanghai, and then go to Saigon BUT with the transfer through Guangzhou?

I am Lithuanian, a holder of EU pasport. I have a flight from Seoul to Shanghai, where I have a transfer for around 60h. I will be stay in the city during these hours. From Shanghai I fly to Saigon, as a final destination, BUT with the transfer in Guangzhou for around 9h, where I am not planning to leave the airport. Will this route work? Am I allowed to enjoy the 72h transfer policy in Shangai and then in a couple of days fly through Guangzhou without leaving an airport? Or shall I purchase a ticket from Shanghai to Saigon with a transfer through a different country (Malaysia, Philippines..). These are no direct flight form Shanghai to Saigon.
SEOUL-> PVG ...60h... PVG -transfer in Guandzou -> SAIGON