pineteam
Unfortunately in FCOM the words of wisdom are scattered in many places so it becomes difficult to fully understand a system especially like the auto flight. This is what I found in one place.
The flight crew should rely on the ND for short-term predictions. It indicates what the aircraft will do under the currently engaged modes (selected or managed). The flight crew should rely on the MCDU for long-term predictions, when managed guidance is active or about to be reengaged.