All, what I am learning is that the
entire horizontal stabilizer is moved up or down to trim the aircraft for attitude and airspeed. This is not the case in small aircraft where a separate trim tab control surface does this. So there is not a separate trim tab per say.
If the above is true then if somehow locked in the nose down attitude then I can see how manual inputs would not work. Do I have that right?
Yeah that's the way I understand it.
The slot shows total trim adjustment. So if you imagine the whole horizontal stabilizer leading edge up then you can imagine how little the full back on the yoke elevators trailing edge up can do to counter it.
Probably just creates a pocket of turbulence.