Good move
Long census data was/is mostly being collected for business, which has resulted in the census being yet another subsidy. Business should pay for it's own data collection and not have access to the power and threat of imprisonment to collect it.
But Australia would do well to look at Canada and how the opposition can spin changes to mean almost anything and touch a nationalistic pride in those new to Canada. For some filling out the form meant they were Canadian. Others recall when they couldn't say they were Canadian on the form and see it as yet another flawed method of collecting data the government already had. Fodder for anyone wanting to attack the changes, or just attack.