"Is the passenger list that has been published a list of passengers who booked a flight or is it a manifest of passengers who boarded the flight?"
At KUL every departing passenger, quite rightly, must produce a Passport AND BOARDING CARD before boarding a flight. Also, at Check-In, a Visa for the destination country is required. IF an Italian travelling to PEK without a Visa is checked-in, then there MUST have been evidence in an eticket or otherwise, that a connection to be made within 24 hours was made. So that should not be too difficult to trace??