No nav, but you're hitting on exactly what the issue is. The screen brightness does adapt to ambient lighting in the sense that the screen dims when the headlights come on (easier to see if the cabin is dim at night). The issue is that even when the computer has all of the displays dimmed in low-light conditions, it will still jack screen brightness back up to maximum when you throw it in reverse. Once you drop out of reverse, screen brightness returns to normal.
Screen brightness is flipped to its maximum under all conditions - day or night, manually dimmed or un-dimmed, headlights on or off.