I have wondered the exact same thing. Google searches send you straight to the wiki article or australian weather forums! Hardly the most reliable information out there (though still great for info). No hits in google scholar or web of science so it doesn't appear that any papers have been published regarding this event. Looking at the analysis charts posted I have little doubt that this day was a significant weather event for parts of eastern Australia. I am also inclined to believe there was a strong to violent tornado that day (otherwise everyone wouldn't be talking about this day would they?). I would like to see the BoM report, is it publicly available?
Besides a lot of trees and a tractor. it doesn't sound like it hit much. Throwing a two ton tractor 100 m is certainly impressive. Would that alone suggest that it was an F5? What was the extent of the tree damage? Just large branches snapped or were trees debarked?
I whole lot more questions than answers.