But both sources of info indicate that duty free purchased before departure in HKG can be taken onboard:
Direct flights from all other countries
For return flights to Australia, you may carry duty free liquid, aerosol and gel purchases on board if they are delivered to the departure gate at the last international airport you travel through in a sealed bag with proof of purchase and collected after you have proceeded through security screening. The application of these procedures may vary from airport to airport and you are advised to check specifics with your airline.
Liquids, gels and aerosols purchased from duty free stores in Hong Kong airports, located after security screening points, will be allowed onboard, however, once purchased, they must be delivered to the gate by Duty Free store staff. The Duty Free goods can then be returned to the passenger once they have passed through the secondary screening point.
Are the Duty Free store staff too lazy to bring the items to the gate?