I too am under the impression that above 10-20 MPH the fans turn off (unless A/C is on). No freakin' way do they blow air faster than 20 MPH. And yah, the ECU has speed data, so it's not that hard to imagine.
Maybe Nissan didn't do it this way on these cars? Plenty of cars turn the fans off above a rolling speed though from what I have gathered.