I have a theory about audiophile which is just that, a theory. It is based on our senses coming in varying degrees of sensitivity. Not hard to grasp, as for vision any eye doctor knows some patients see 20-15 and can read with accuracy small text that a 20-20 person can't. There also is research pointing out we humans come with varyious density of taste buds, which is why some people need hot spicy food to enjoy it (low density) and some become professional taste testers (high density). The rest of us sit somewhere in the middle.
So my audiophile theory goes like this: Some people hear better than most. They simply have a better capability to detect and process sounds than most of us. Add that there are also better listeners. This may come with age (just getting older), experience (listening to ALOT of music), or training, or all. Age also works against us. The high end of what we can hear diminishes when we get older. Google "mosquito ringtone".
When someone claims they hear things we can't hear, we dismiss their delusion as impossible simply because we "know" everyone hears the same. If we allow that there is a range of capability among listeners, then we have to allow that a few are more capable than most. Google "bell curve":
Just a theory.
But you wouldn't believe someone if they said they could see something that required 20/1 (or better) vision to see, and the detail claimed to be seen in fact is finer than the capability of the printer for the test chart, would you? Because that's the audiophile equivalent for a lot of contested topics here and elsewhere...