You don't have to have the smaller part on the right with AA.full screen would be amazing BUT when the split screen setup (Coolwalk as they call it) of Android remains 1 bigger part at the left and 1 smaller part at the right, it is still worthless.
It would be nice if you could have e.g Waze on the top part and another app on the bottom part and not side2side.
And imagine a time where only having half of a 12" display for navigation is "worthless". There are still people using older 4" display stand alone navigation devices, or their phone screens for Nav. Both much smaller than what we already have in a split screen.