It is the usual practice on most cruise ships for luggage (other than hand luggage) to be put outside your stateroom for collection the evening before you disembark, so even if you collect it from the quay immediately on disembarkation it will still have been out of your possession overnight.
Not saying it will but you may find the practice differs in Beijing. It did some years ago when I was there. .... Neil.
Why not call Princess or your agent for an answer?
I have done both. Travel agent tried 4 times, answer was always "waiting for LA to reply. Eventually on Thursday Travel agent rang to say no problem they had been told eventually that I could have my luggage during the Hotel stay. Friday this changed again to "no I cannot take my luggage". They have communicated through my TA. Letter and phone call remain un-answered. The office at Southampton refer all questions to LA, I think by pigeon post. This is our 12th cruise in the past decade but only the second with Princess, and the first left a lot to be desired. RCI and Celebrity seem better organised.