Applicants should know how they performed in the assessment with justifications for the overall results. So apart from the debriefing issue, I do believe the whole program is fine. And I think the word "dodgy" is an overstatement. GAA did not promise any debriefings or refunds, and all applicants did accept that.
GAA are still involved in the selection process, albeit with some help from OAA.
Certainly not. It's the other way round! Technically speaking, OAA is responsible for selection with only some help from GAA. Once OAA has selected the proper candidates, GAA tells who to go now and who to go later. They are the customers as you have said.
Remember that OAA is regarded as the best FTO in this sort of business, and surely they don't want to hurt this eminent position by accepting cadets who are below their well-defined standards.