The trim release is not actually part of the autopilot, it is simply a cyclic centering device.
BONG! WRONG!
The autopilot moves the cyclic via the force trim system - if force trim is not engaged, the autopilot is feeding inputs to the force trim, but if it is not connected to the cyclic, nothing will happen.
Force trim without autopilot is simply "stick position hold", autopilot without force trim is just using up its computing power, but put the 2 together and the machine responds to autopilot inputs.