I've always wondered why they chose those specific spots for the cameras and that amount. To me (not an expert), it would seem like having the two front bumper cameras that are shown in the picture would have been a more ideal location than a single low mounted front bumper camera. But how you would integrate them in a seamless way with the body, and not have them constantly blocked by road grime, is beyond me.
That said, I also wonder how much this will aid with cars that don't have any front bumper cameras at all, but are still HW4 cars. At this point, it seems like it would be more accurate to call cars with front bumper cameras HW4.5 or something along those lines. It seems that those front bumper cameras are slowly becoming more integral for FSD, and might be a limiting factor to enable things like banish in the future. I could definitely understand if just the high mounted front facing camera is enough with good training and ground truth data. But it really brings to question, if the high mounted cameras are enough, why are they testing this specific camera setup and in those locations on the car? Will banish be exclusive to those HW4 cars that have front bumper cameras? I guess time will tell.