Not true: https://www.legislation.gov.au/Details/F2020L00306/Html/Text
"An Australian citizen or permanent resident (the person) must not leave Australian territory as a passenger on an outgoing aircraft or vessel on or after the time this instrument commences"
https://www.bbc.com/news/world-australia-59058945 "Australia has confirmed it will lift a ban next week that has prevented its own citizens travelling overseas without permission."