Would say that SAW would have had the SON WX, it would have to have been one of the flight plan ETP diversion airfields. Somehow I would think that SAW would not have got that wrong!!
Also if an immediate diversion was required to make SON, no problems with the legalities there, at least the fuel is there for the approach and the divert ............anyway appears you answered my question, one shot and still have the fuel for a 650mile divert, not bad after what must be almost a 3 hours flight.
Regards Munda as an alternate....that would have to be an issue with CASA surely, Airline Ops approval is their domain and as they do the approvals, surely, they would have monitered the divert destinations.