How though? You can still purchase duty free on EU ports and DXB.
The only difference is that the duty free purchases will be placed in the bulkhold for the Dubai to Australia flights.
This is what happens for all EK flights to Australia at the moment.
I am talking in general not specifically the arrangements in DXB and maybe I being a little bit cynical and flippant.
The way I see it is Australia is imposing rules over and above what more or less everyone else is doing for what ever reason.
For example why does duty free purchased at the airport the flight is leaving from, that is in a sealed bag have to be delivered to the gate (forget the US here because in their case it has always been the case and is because they don't separate domestic/int departures) or in the case of DXB put in the hold. Why is this only for flights flying to Australia. For example if I go to Bangkok and fly to the UK I can take duty free over 100ml purchased in Bangkok, but buy the same stuff from the same shop and it cannot be taken to Sydney, simply because Bangkok won't deliver to the gate. So liquids in transit I can half understand, but not liquids brought in the airport the flight leaves from.
As I said maybe I am being cynical and flippant but I would say the duty free shops and Australian airports have had a part to play, making it 'harder' or putting doubt in the minds of travellers to buy OS, but on arrival in Australia you need to walk through a duty free shop to get to immigration or you can buy when you leave and collect on arrival.