I think what Paul is describing is a simple SAS system that has a trim system to stop the cyclic flopping over and to give a datum to work from as well as feedback for the pilot when pushing against the springs - all the AP is giving is rate damping rather than attitude hold.
What AC is describing is a more modern and complex autopilot where the trim system is an integral part of the AP so that when the series actuators reach their limit of authority, the parallel actuators in the trim system can move the controls (open loop) to redatum the series actuators, thus enabling attitude hold and other higher AP functions.