This was the only real lead as far as the CFI check goes;
The CFI was not rated in aerobatics, and the check flight was limited to an assessment of the instructor’s general handling and area knowledge.
Really shows as to the limitations of hiring a contractor because you don't have the required approvals. The CFI possibly could have asked about spin recovery techniques, possibly not, its not in the notes. That being said the CFI was not aerobatic endorsed and the instructor showed a high level of general ability, which made them think he was competent across the board (I'm not saying he wasn't or was). I always thought that CFI/CPs had to hold all the endorsements and ratings conducted at the school, however the lack of ATSB mention about that makes me think its not a requirement at least anymore. I think it would have been more appropriate that the CFI possibly get the instructor to conduct one of the sequences for which he was contracted for, in hindsight you would think spinning being the obvious one that will be focused on from now.
As for the instructor, you don't know what you don't know. Read that POH and ask questions from mentors and others with type experience even if the aircraft is very similar to previous ones you have operated. There are no stupid questions in aviation.
Even in the airline business I ask previous crews 'how's this thing going today' which is the casual way of asking what little menaces it threw at them for the morning so I can be prepared for it, and that's flying the same type over and over. Even between airplanes in a single type they all have their quirks and nuances.