Ed, I don't think that the definition of being QAA is being changed. It is simply adding onto that level of achievement with another "interim" level. There would be two reasons to do this, I think. First, AKC will add more revenue from those who continue to compete in the Q. Second, it will give the incentive for an interim goal for those who are not yet ready for AA, and/or may be getting experience for higher aspirations for their next dog.
I know of one dog who got a JAM in the Am in a rather small trial, which made the dog QAA. The dog is a really good dog, but it was really a lucky day for him. He was not yet up to the capability of being a consistent finisher in AA stakes. I know of another dog who became QAA with a 2nd in an O/H Q ... and then also went on, a couple of months later, to take a 2nd in a "real" Q running against the pros as well. This owner felt that the O/H Q was just as demanding as the "real" Q later. While the O/H Q was had a smaller entry than the "real" Q, there were not many who finished the trial. The winner of that trial was a first-time-in-a-trial handler and dog ... while older, more experienced dogs and handlers were not up to the task. Yet, I also know of a handler who took a 2nd in an O/H Q who felt the tests were easier than they expected (the handler having run only MH with a very consistent record in MH passes). All three of these "anecdotes" involved dogs between 2-1/2 and 4-1/2, so not the scenario John might expect of "also-ran" FT dogs achieving the QAA when they were past their prime. Surely there would be some instances of that occurring, but it remains to be seen whether that would be the majority of outcomes, rather than the minority of outcomes.
Then, we also have instances when handlers double-staking Q and Am insist that the first series of the Q was more difficult than the Am. That doesn't necessarily make most people assume that an Am placement or JAM should be "discounted".
Since there are so many variables in a field test, it would be hard to define the testing/judging tightly enough to make it like formal obedience. Even in formal obedience, where the tasks are uniform and the exacting precision approaches neuroticism, there are dogs who can achieve identical scores, yet the one dog does so with style and another offers no excitement in the performance. It doesn't take long before breeders and fanciers figure out the differences in those individual achievers, and then make their breeding or puppy-buying distinctions accordingly.
FWIW, in obedience, the majority of competitors are owner/handlers, so in that respect the playing field is pretty level. However, just as in field, not all owner/trainer/handlers are created equal When competing in the "B" classes, the "amateur" handler will face off against experienced trainer/handlers who are known for being highly-respected instructors through seminars and DVDs, etc. Even so, and even though the tasks are highly stylized, there are days when the "professional" trainers' dogs will falter, and the "amateur" will succeed.
Another thought occurs to me. The judges for field trials have to be amateurs. We trust them to know and reward excellence when they see it. Through their experience in training, competing and judging in field trials, these judges have seen many great dogs of all the breeds; and they have seen the not-so-good. If John or Ed are judging, I believe that those who would run under them would be honored to do so, and trust their judgment. It wouldn't matter what stake they were judging.