Currently, Australia has tough restrictions on liquids for both departing and arriving flights. These mean that for a flight to Australia, you will be re-screened before boarding the plane, with liquid restrictions in force again at this point.
As we saw with an earlier question on Kuala Lumpur airport, this is that you can't buy duty free in Europe and take it with you to Australia on a "direct" flight, as you won't be allowed to take it with you through security when boarding the 2nd part of the flight. (Your only option would be to only check your bags as far as the change of planes, then collect your bag, clear customs and immigration, put the duty free in your suitcase and re-check. This'll only be possible on a long layover, and is impossible on the usual 1-2 hour stop on most "direct" Europe to Australia flights)
At some airports with direct flights to Australia, it's possible to purchase duty free at the airport, and have it delivered in a secure way for collection at the gate. (This is different to many airports, where they put your duty free in a bag at the till and give it to you, and may be something they only do for Australia flights). At other airports, they don't offer this, so you're unable to buy any duty free liquids before boarding, and have to buy them (at normally much higher prices) on arrival in Australia.
What's the situation at Hong Kong International Airport - can you buy duty free liquids for delivery to the gate, or are Australian-bound passengers unable to buy?