What if the aircraft climbs rapidly on the autopilot with a lot of power. Than the AP captures altitude quite abruptly. It has to pitch quite hard nose down. The stab is trimmed hard nose down and at the same time power comes agressively off to keep level. Than AP disconnects. Stab is trimmed down. Power goes back. It is a huge nose dow moment.
You try to pull the yoke, but the small elevator is aerodynamically hidden behind the huge stabilazor. You try tu pull, but nothing happens. At the moment you have too options. Either add a lot of power to get the nose up or trim fast like hell. I am not a Boeing pilot. Does that make sense? May be trimmimg would not be fast enough to get yourself out of it. You would probably need to add a lot of power.