My position is this: if you have a headache, do a Google search for a few minutes, "diagnose" yourself with brain cancer and then you lose the headache after drinking water, you haven't cured the cancer but you've simply fixed your dehydration.

I think the position is different. Symptoms can have many causes. You can undo symptoms due to some causes by doing some things. That means you can cure the condition that's expressed via a symptom by doing the thing. However, that doesn't mean you can cure the symptom by doing the thing.

A personal example is shortness of breath. My friend and I both had that when we were kids. However, I had it because I got bronchitis for a bit. He had it because he was asthmatic. Imagine if I said "Oh, I don't understand what the problem is. All I did was rest and it went away". Well, that won't help my asthmatic friend, will it?

Less charitably, it sounds like gatekeeping.