It's hard to know what was on his mind with that low and slow comment. Maybe he had been blindsided by the ABC journalist commenting on the subject matter then immediately asking for a reaction; that's the worst position to be in when there's a news story. Better to be the one doing the initial part of the story.
I can see the possibility of ATSB handling a collision in a CTA circuit because of the complexity of key radio calls, correct circuit position, correct approach, correct choice of runway, failure to hold, wrong runway (on dual runways) etc, but even than doesn't take too long for a Recreational Aviation investigator to learn.
If you look at the exhaustive procedure ATSB uses, even if they had a graded policy for top of the range RA with electronics down to a trike there just has to be big blowout in costs for not much return.
On the other had it was RAA which submitted a list of engine failures one of which was a flat tyre, so maybe RAA has some work to do which would satisfy the complainants.
It would be interesting to see if the trike guys out at Marian even know about this and what their thoughts are.