With respect, some of us have bought a car having been promised this feature by the salesman and the Nissan brochure.
The feature is most definitely there and it applies for about 3 seconds before dropping out. To demonstrate: sit stationary facing uphill on a reasonable incline, in 1st gear, clutch and footbrake depressed, handbrake off. Lift footbrake to apply gas and do this lazily without bringing the clutch up. Would expect the car to start rolling backwards immediately on lifting brake but it does not. The car will just sit there and then after a few seconds, suddenly, the car will start to roll backwards.
My issue is that it does not *always* apply and so being lazy I will roll backwards.
Same can be demonstrated in reverse facing downhill.