Can I clarify please? Australian citizen, living overseas for 10 months and fly to Australia (quarantine for 2 weeks), 2 weeks visiting relatives, then exit back to overseas. Exemption to exit needed?
Your guess is as good as mine. In theory, no. Presumably as they initially departed under exemption to move permanently (from memory you've discussed the departure 10 months ago?) , it should be easy to see they had an exemption to leave permanently then and the 12 month (rather than 24 month) rule applies.
Have pasted below from relevant part of home affairs site, highlighted the ambiguous bit in red.
Ordinarily resident
You are considered ordinarily resident in a country other than Australia if international movement records show that you’ve spent more time outside Australia than inside for the last 12 to 24 months. You do not need to carry a paper record of your movements with you. If required, Australian Border Force officers at airports can check your movement records in their systems.
If you do not think you need a travel exemption, you can present this evidence when you check-in at the airport. However, if you have any doubt about whether your circumstances fall within the definition of ordinarily resident, we recommend you lodge a request for assessment at least two weeks prior to your intended departure.