Not sure which route(s) are marked this way, but over here, turn signals are required for every turn and every change of lane, so the map would get extremely cluttered with these warnings.
A little bit of googling shows me the law in NJ is not much different from here:http://www.njlawman.com/new-jersey-traf ... -4-126.htm
The only route where I would not use my signal in this intersection is from SW to N
(and reverse). Are the signals required for this route?
And, like with speed limits, the driver is always responsible for his own actions and should detect the road signs by himself. A GPS system is a routing aid, not a driving nanny....