If they had a flight before their visa or stamp expiry date and it got cancelled and rebooked, and is now after their expiry date, they can get 30 days with a letter from their embassy. (Provided the embassy agrees, so contact them)
If you need the 30 days, then get the ED cancelled first, but as Robert says it cab only be used for 1 entry anyway....not sure where you would border bounce though......options are slim..
Did you see the 🤣🤣🤣 at the end of his comment ;) Nobody in their right mind should be travelling to China. It will put you on just about every blocked list there is :(