That's a big problem with Aviation, those outside of it think that an airline pilot is an expert, when that on it's own means nothing to other areas of Aviation. At least the Qantas pilot is further qualified as having held a senior training position, although that still means very little if they have not had extensive experience in GA/RAA as an instructor with initial training knowledge.
I'd hate to say it, but it's the same as having two bus drivers of unknown background as expert witnesses on a motorbike accident. That being said I would trust the QF pilot at least having some form of training background to make an assessment of the training records. We don't even know if the Bonza pilot has ever trained/instructed in his life.
However, Mr McKeown added it would have been "very important that he only operated in conditions and on tasks commensurate with his ability".
Now this is an interesting point, possibly key to whether the training was adequate. Was the pilot aware of his own limitations? Did the training make sure that not only the pilot had the required skills for the level of certification, but also the training included knowing what they were not capable of, where they should draw the line. The basics of air law in GA focus on legal privileges and limitations, which also includes weather limitations and so on. The limitations are the finite limit of what you can do with the licence/certificate and in what conditions and then the candidate should have it ingrained that the legal limits are far lower than you should venture, set higher limits to prevent you going below them "
commensurate with his ability". Finally was there any notes in the training files that specified the candidate had any further limits and what those were.