All that you have suggested to yourself is that self-hypnosis works.
When the water is very cold or very hot, then the heat / cold sensor goes off scale for the brain and it ceases to distinguish it, because this is already painful shock, not a feeling of warmth or cold.
And you pour water not from the tap, but from a teapot pre-boiled. Let's see how you will represent boiling water with cold water. Blah blah
It seems to me that this case is associated with a very strong self-hypnosis. Try something else. For example, the opposite effect with cold water. But still, the fact is that the water is not hot enough)