ubersapianthats a load of absolute crap, asus what the hell.
Just got some feedback from asus australia and according to them there will be no support for VoLTE in the foreseeable future at least here in australia .. They are of course throwing the ball back to the australian telcos who have supposedly not certified the ROG 3 device for VoLTE services ... Pretty funny how Telstra for example have told me a number of times that they dont whitelist/blacklist any devices anymore and should the device support it it can connect to Telstra VoLTE.
Running a thrid party ROM at this point in time might be only way to get VoLTE settings working on this device.