I agree with your comments on reversing cameras as I prefer to rely on my side mirrors and rear parking sensors. But my new Infiniti Q50 hybrid has an issue: once I've selected reverse I must have to wait a full 12 seconds before the sensors will activate. That's a bit late for the poor person or object behind. The dealer simply points to the handbook and says it is "a driver aid and should not be relied on". Maybe you would get a better response from the manufacturer on my behalf.
Infiniti spokesman Peter Fadeyev says: "The car has a computer with an Intel processor, so it operates like a personal computer on start-up. The camera still comes up but what is missing is the audio for the sonar. So the owner can still see behind him with the camera."