Here is what he explained, and what I checked myself afterwards.
Hours asleep is not the same as feeling rested. What makes you feel rested is deep sleep. That is the stage where your body does its heavy repair work and recharges your energy for the next day. Harvard calls deep sleep the main time your body renews and repairs itself. Get too little of it and you wake up flat, even after eight hours.
And you only reach deep sleep when your body fully lets go. If your neck is bent and your spine is twisted on a bad pillow all night, your muscles never switch off. Your body stays a little tense, a little on guard, and it never sinks all the way into the deep stage that actually recharges you.
So I had been pouring supplements into a body that could not relax in the first place.
The way my mate put it stuck with me. Supplements work on your chemistry. They cannot straighten your neck.