My autopilot does an amazing piece of work flying the ILS of course it pitches for speed and I have to use thrust to control the descent
As stated both arguments are not correct.
Take the situation where you are on the glide and hit a bad area of sinking
Air. You are now low and slow do you pitch further into the trees for speed or use power.
It is all about managing the energy available to you from the power unit and airframe and being aware of how to play both.
But the less engine power you have right down to no engine in a Glider the more pitching for speed takes dominance
Pace