They do report if the camera can't get a good image. Glare from the sun is the most common reason. It is certainly possible that there is a window between when vision is degraded enough to be dangerous and when it alerts the driver, but a single occurrence isn't proof of a widescale problem. That is the type of thing that should be investigated in more depth, but it is hard to get anyone to care when it is only a theory that isn't even yet connected to a single accident.