Hi Denti, that's not quite correct.
With speed reduction, the autopilot will command pitch changes to maintain altitude. These pitch changes (up/down) will be seen on the active sidestick.
In fact, you will naturally expect to see these pitch changes, because if you were to fly the plane manually you will make those same pitch adjustments.
Over time, you start to develop an intuition of how active the sidestick should behave in different flight conditions when on autopilot.
E.g., in good weather straight-and-level flight, you would naturally expect the sidestick to only show continuous small movements corresponding to small autopilot corrections.
So if you happen to notice the autopilot commanding large and unexpected sidestick movements, then that might be an additional cue to you that there's something which might need your attention.
Today you might not have any indication of trouble until the autopilot gives up and disconnects.
This is not to suggest that you monitor the sidestick. However, as mentioned, having an active sidestick can provide additional visual and tactile feedback that's natural to the pilot -- almost at the intuition or sub-conscious level.