Nitpicking, but a quick look at recent Hotham arrivals on flightaware shows that tracking stops at a position roughly coincident with where tracking stops in the ATSB report.
Its too long ago to check again now, but I have a strong recollection that at the time, Flightaware showed VH-OWN in the area of the traffic conflict. Maybe not approach, but the traffic conflict that triggered this investigation was not in the approach area.
The report (characteristically for the ATSB) does not give enough data to check against their commentary. the ATSB is really good at switching between time, altitude and map location in a way that does not allow checking of their re-construction. The positions on the approach plates only have altitudes and not times, but it looks suspiciously like they did have tracking data for both aircraft during the time the report says they do not. It interesting that they show Est Sale radar screen shots, but not AsA radar screen shots. Nothing can be correlated.