Flying opposite of how an autopilot/autothrottle works doesn't seem logical. Speed gets low the autothrottle increases power. Autopilot gets high it lowers the nose. It doesn't matter if it is in altitude hold or following a glide slope.
Just as with manual control, it's not that simple...
Autopilots and autothrottles work together in autoflight to make very small incremental changes. Each change in one system will trigger a change in the other. Note that in VNAV climbs and descents, the announced pitch mode is often VNAV SPEED, where the elevators and stab control the speed...