I think the diagnosis can be mis-used, and applied to anyone where doctors think they should be fine from whatever tests have been run. Or if doctors just aren't familiar enough with symptom patterns in individuals. If it is a resonable diagnosis, then it should be able to be confirmed somehow.
To me, it only makes sense when there is no objective evidence of reflux (such as no inflammation in esophagus).
I have been diagnosed with it, and tried the treatment of two psych meds. Neither of which did anything except give me the drowsy side effects. That's why I don't think it's necessarily a reliable diagnosis, I don't think it fits in my case. If hypersensitivy was the issue, then decreasing sensitivity should help it, but how far does one take it? Yes, I can take a prescription painkiller and the sensations won't bother me as much. I don't think it's too far different from someone with pain from an injury.. you can numb the person to the point where the pain is less, but it doesn't follow that the injury is not sufficient to cause pain in the first place (therefore the body would be hypersentive to the injury).
From what I've read about it, sometimes it's written very broadly as "symptoms" related to nonacidic (weakly acidic) reflux. But there are truly so many symptoms of reflux, from pain, to bitter taste, to tightness, I don't think all of them can be lumped together to indicate hypersensitivity.
There is published evidence of people with normal DeMeester scores, objective evidence of reflux including hiatal hernia, who partially respond to PPIs, who have full resolution after surgery. I had surgery 7 weeks ago and I'm hoping to be one of them. All these people would have the label hypersensitive since their DeMeester is normal, yet removing the reflux has helped them (and I think is helping me, as my healing continues).
I don't know what a typical 24 hour PH study looks like for someone who is on maximum PPIs. But if acid is well controlled and the person still has symptoms, many of them get fundoplication, without ever getting tagged as having hypersensitive esophagus.
In case you can't tell, I don't like the widespread use of the diagnosis :)