With the std nav, what happens on main screen when the nav map is displayed on the AID? I know for sure with the std nav unit you can still show maps on the AID.
When you are in Navigation mode and show the map on the Active Info Display, you cannot show the same map on the main screen. However, you can show another view on the main screen (eg. radio, CD etc. ) if you want to (and keep the map on the AID).
Unless you are actually following a route (ie getting route guidance), then yes, the main screen is blank if you press NAV.
However (and this is a pretty good function), if you are actually following a route, and the map is displayed on the AID, the main screen shows a list of the next 3 turns you need to take, and the mileage to them. This milage counts down as you approach them.
So yes, not having the map duplicated may seem an issue, but you can always display something else on the main, and, if actually following route guidance, you get additional directional information on the main screen.
Note that if you are showing the map on the main screen, one of the button options is to toggle between AID and main screen.
Hope this makes sense......