I think what is being lost here is that in all the examples of pitch for speed what ia actually being described is trading flight path angle for speed while maintaining a fixed thrust. This is not the same as controling flight path angle with pitch and controling speed with thrust.
So the example I like is fixed flight path angle. now tell me how i control speed using pitch?
Correct. I cant. I must change the thrust.
Whenever a specific vertical path is required we have to change the thrust drag ratio to change speed and that requires a change in thrust.