I come back time and again to the difference between reasonable and recommended. A recommendation in medicine is something you would be unwise to ignore as a doctor. Reasonable is something that you as a patient should do. A doctor is going to tell you all the recommended things because the way medicine works is all around what is shown to a reasonable statistical level to be a good idea, or at least seems that way. They will still recommend some things that are nonsense and they will still make mistakes, but they won't be sued.
If you try something and that works for you then you have a sample of one. It may have done nothing and the problem resolved itself, it may have solved the problem, it may even have slowed your recovery, but if you have the same problem again it is fairly reasonable to do the same thing that seemed to work last time. It isn't proof, but it is reasonable to try again.
Does having a kebab on the way home from a night of drinking actually prevent hangovers? Well, maybe, it does have salt and that is depleted during drinking, but is a doctor ever going to recommend that? No, never.
Yeah, I agree with your thoughts on the 95% thing. Its like with pain management. I am completely non responsive to morphine. Most people respond well, it just feels cold in my arm and that's it. When I flayed my wrist they gave me tonnes of morphine, the maximum dose I could have, and I had almost no effect at all. I got more from the paracetamol they gave me after that which was good because they had to remove my temporary dressing from a very large open wound and any relief was helpful. Now I just ask for aspirin and paracetamol, though after a wonderfully fun heart infection I can't use aspirin for pain relief without considerable bleed risk. Oh well, paracetamol it is.
But yes, if I go in for emergency care and tell them "no morphine, paracetamol only" they will probably not take it seriously without a doctor supporting it. Good thing I have a fairly high pain threshold.