I'd actually rather have the device tell me to turn around at a convenient place. Finding a place to safely go the other direction is part of learning how to drive and the exam anyway, and how to do that is at the discretion of the driver. Could be a U-turn, could be a roundabout, could just be going into a side road and using a drive way. But as you note, the map data rarely has the information where is possible or allowed.
