What I am trying to point out is, not all inspectors are bad/incompetent/whatever. In my case I was able to tell him what I wanted photographed/inspected. His opinions were noted, but not relied on by me in making my decision. The photos were relied on by me, heavily. After all, pictures do not lie, right?
I think for a commercial inspection to be of value one has to be able to direct the inspector in terms of what to inspect and photograph. Many inspection services do not allow such. That they do not is a red flag!. Some only allow communication with the inspector after the inspection has been completed. Another red flag. Some allow no one-on-one communication. You get a report and that is it. Run from such entities!
Of course, we all agree that doing your own inspection is best. That is not always possible. When it is not, we want someone who is knowledgeable with respect to old rides, and the particular marque.
That said, even if I hired/asked Matt Harwood to look at a ride for me I would want to tell him what to look at and photograph. If, when doing so he said, "I know what to inspect and do not need your directives," well, I would be looking to find another inspector!