Let me put it like this. In a average 12 month period, the Australian government, the minister and the department will make over 2000 changes to migration law, rules and regulations. Out of that, the department will maybe publish ten on its web site.
It is not unusual for its website to be totally wrong. It is also very common for the department to give incorrect information and over my years I have come across masses of people who have caused themselves massive issues because of this.
At the same time, the department has a legal indemnity for this. In other words, you can rely on their information, apply for a visa, get refused. There is nothing you can do about that. You can of course complain, at which point the department will simply point out that you should have consulted a registered migration agent.