Dick The Tenerife accident was the result of a lot of HF considerations especially the concept of cockpit gradient which would not have been present in Benalla. I am not saying that there are no HF considerations but you originally asserted that the ATSB do not understand HF and that they have no expertise in this area. As an airline pilot I am resonably familiar with the two crew environment and its limitations. I also know that if I go up in a light aircraft then I take a professional interest in what is going on around me. If something like a GPS receiver was giving warning messages I would ask the pilot what it meant. You can't make the assumption that a pilot would deliberately ignore a warning in the absence of any other evidence such as a CVR.
Why aren't you still pushing for the installation of TAWS equipment for turbine aircraft of 6 seats or more? That equipment would have gone a long way to preventing this accident.