Unless autopilot design has fundamentally changed since my days, the (pitch) autopilot would have no way to 'sense' an uncommanded power loss.
It did its job, i.e., keeping the aircraft on the 3 degree glideslope by increasing pitch (and thus AoA) until things got too hairy and it disconnected.
It 'expected' the autothrotlle to keep the speed up.
CJ