Theoretically this is true. But right now there are VERY, VERY few destinations that don't require consular support to get back from. The chances of any traveller right now being able to say that their return flight will definitively be operating is practically nil. 170,000 Aussies have sought consular assistance worldwide in the past two months in order to get home. And more still who have technically breached visa conditions because there are no flights. Yet Australian embassies worldwide are still dealing with people saying "but I didn't think 'Do Not Travel' would mean I wouldn't be able to get home from Bali/Aspen/Phuket/Chamonix".Yes. When the Do Not Travel alert went on it never occurred to me that this prevented travel out of the country. I thought you could still travel but at your own risk completely.
There's a biosecurity aspect to it, but also an allocation of resource. As I mentioned in the other thread, DFAT are scaling back everything else to prioritise getting people home. This includes scaling back support for international trade at a time when international trade is being completely thrown on its head. You do what you can to help people who have found themselves in strife through no fault of their own, but prioritising the restart of trade has to be in the national interest ahead of supporting those that would choose to ignore a 'Do Not Travel' warning. This is not forever, but it's an extraordinary circumstance.