It's not quite that. There are really three triggers for this message so far as I can surmise. First, a camera malfunction that isnt detected by hardware (so it appears to be working to the software stack, but isnt). Second, a blocked camera (dirt covering camera etc). Third, a camera that sees only black because basically that's all there is to see.
I think the point is that the software cannot tell the difference (nor can I see how it could). Basically its saying "My AI/NN cannot make out any recognizable objects" and assuming (for obvious safety reasons) that this might mean the camera is blocked/malfunctioning. And as soon as it
does see something it corrects itself and the warning goes away. Fo a camera blocked by condensation, this happens as the car/camera warms up, for a blackout this happens as you drive to a place where lighting/traffic gives the AI something to snap onto.
As for radar, this would not make any difference. Even if the car had radar/lidar/magic pixies, it is still going to have to tell you if a camera is blocked (as it should). Judging by this and other posts about this issue, most of the faults squarely fall into the condensation or nothing to see categories. So this is not a camera being bunged up with dirt; its just that its winter and cold and dark