I haven’t yet found the flaw in ATSB reasoning, but I used to do something like this sort of work years ago.
While I may well be mistaken, ATSB has come to some what appear to be startling conclusions;
1. Angel Flights are seven times more dangerous than ordinary private operations. These private operations themselves are more than twenty times more dangerous than charter and RPT.
This implies that Angel Flight pilots are seven times stupider than the general GA pilot population or, as ATSB seems to suggest, there is a reality distortion field around ATSB operations that makes people idiots (seven times stupider!) when operating an Angel Flight.
But wait! There’s more.... Table B5, Technical occurrences, shows that the aircraft knows it is on an Angel Flight compared to a private flight and being malevolent, responds by making things break or fail in flight. The possible exception may be the engine, which seems to be non sentient and fails without regard to who is driving or where they are going.
Then of course there is the weather, birds and wildlife, all of whom seem to have it in for angel flights.
I have to say I am not convinced because “category of operation” is a rather imprecise term. We are not comparing apples with apples I think. For example a private operator doing dozens of scenic s from his home airport is not exposed to unfamiliar airports and less than perfectly sunny weather. A fairer test would be to look at private flights that match Angel flight trip durations - say four hours there and back and compare those safety occurrence records rather than comparing angel flight with someone doing circuit training.
Anyway, that’s my opinion FWIW.