I am convinced as to the authenticity of these reviews. Unlike so many online reviews of everything from blenders to cars, there is no doubt in my mind that the above reviews for these devices is accurate and based on actual use and sincere and knowledgeable attempts to get the best performance.
So, why the difference in results? With typical online reviews that vary, something is at the heart of the differences. Some people get a defective product, some people don't read the instructions, some people have unrealistic expectations, and some have legitimate (but different) needs. In the case of these devices, none of that applies. Basically, everyone got them for the same reason, expected the same things out of them, used them properly, had "good faith" in their hearts throughout the whole period.
The main issue seems to be the ability to separate out noise from useful sound. My hypothesis is that this aspect of performance is not related to the device. There is something about each individual that determines how well noise and useful sound are processed.
Until recently, the last 10 years or so, I have not had an AN. Based on the size and time of diagnoses of my AN, it is doubtful I had an AN 25 years ago. But, as long as I can remember I have not been able to understand conversation in noisy environments. Even now, my "bad" ear is 96% voice recognition and only impaired in low and high frequencies typically outside of normal speech. So, even with good hearing and no AN, I have never been able to discern speech well in any kind of group setting.
I don't know what it is that makes it so one person has good results discerning speech and others don't. Why is it my wife can carry two conversations at the same time, in two languages, in a crowded gymnasium, and I can't carry one (and never could) in a small dining room with 5 people in it? If someone could solve this issue, it would be huge and would impact more than the AN community.