I tested it in a Mazda3 2014 at a mazda promotional event a week ago. The test consisted of a small incline with a balloon type object that would mimick a parked vehicle. The instructor was very clear in his instructions : SCBS will only work if the driver is not in control of the car (no brake, gaz or steering input) and between speeds of 4-20 mph.
So for the test, we would brake 10m in front of the object to a full stop, then let the car go towards the object. We'd hit about 20-25 kph (canada). at 6m, the car detects the object and "readies" itself for the SCBS application, and at 3m it applies brakes, so we would be a little less than a meter from the object when the car is at full stop. the first time it was pretty stressfull because you seem so close, but it is designed to work at low speeds so...
A friend of mine tried it on the 6, and said basically the same thing. Hope this helps!
What did you try, exactly?