I thank you all for your contributions to this discussion. I think I get what you are trying to explain, but I am a simple soul and by my logic, any system that works agains my control inputs when I fly manually is making my work harder.
And the STS works when the aircraft is heavy or light, GC fwd or aft, derated or full thrust. That is not how the STS is explained. I have flown the NG since they made it. I have never bothered with the STS before, I simply cancel it with manual trim. I was just when I saw the system discussed that I started to check what it did.
So to all of you 737 NG drivers out there. Next time you take off, fly manually and let the STS work without interference. Clean up the aircraft. Tell me how the pitch controls feel. Let go of them (if you dare) and see what happens.
For those of you saying «just let the STS do it’s job». No. You can’t because it will bring the aircraft well out of trim.
It can’t be the regulators job to make the aircraft trim itself into a situation where if you let go of the controls, the aircraft will fly itself into a stall!