If they paid for a DONE3 and went to Australia, then they indeed got a bargain and I'd be disinclined to tempt fate with an itinerary change, even if the "any place in the Middle East" rule applies. Someone at the tariff desk would need to figure taxes, and that might reveal the error. But the Oz=4 rule is so well known that I'd first examine the tix and make sure the price was actually for a DONE3.