A xONE3 is not possible from Australia due to our need to route via Asia and the even on the one flight number through to Europe (ie. QF1 or 2, BA9 or 10), it counts Asia.
The fare you are referring to appears to be a circle fare which is different to a RTW.
The three continent One World Airlines Circle Fares, only circle the continents Australia - Asia - Africa - Australia or v.v. and an example routing as listed at BestFlights is Sydney - Johannesburg - Capetown - Johannesburg - Hong Kong - Tokyo - Sydney. As you can see, you don't actually travel around the world as with a xONE3, 4 or 5, but just around the Indian Ocean, Asia and back to Australia or vv.