I received an email back from ASUS Australia regarding VoLTE for Australian carriers. Reads as follows:
"They have advised that at this stage no VoLTE scheduled for certification, we are pushing to have telco's test and approve on future phones. Until these newer devices come in and are certified, VoLTE will not be available for ROG Phone 2 and 3. Feedback has been noted and will be relooked at for future certification to see if these models can be tested, updated, and certified as well, no ETA on schedule".
This should be made know to anyone looking to purchase ROG3 in Australia. Personally I will add settings myself, but absolutely amateur of ASUS to make a flagship phone with no VoLTE support and sell it in Australia without pointing that out. Hopefully anyone thinking of purchasing an ASUS phone will search and find this.
Cheers