@Fl1ingfrog
Thank you for your input.
On the approach (and in level flight) autopilots and flight directors use pitch for path and power for speed. In climbing and descending flight (non-defined vertical flight paths) they use pitch for speed and power for vertical gradient. Climb gradient (fixed power setting) depends on speed (controlled by pitch). The laws of aerodynamics apply to all aircraft, regardless of size and regardless of whether humans or autopilots are flying them.