Oh right sorry, i missed the point of your message.
Since the game was under chinese rules, there was no harm of filling those liberties. But about whats the correct etiquette i cant say, OGS does implement situations like this a bit badly. Normally on real board you would play a variation till you’re both satisfied, and then go back to the situation where you both passed and game had ended, but sadly that doesnt work on ogs unless you start doing serie of undos.