But that's exactly the point: there's no general rule for this kind of thing, it depends on the concrete situation. There are definitely stop signs where you need to do a full stop because you cannot see any oncoming traffic. Basically: it's OK to do rolling stops until it isn't.
Same goes for flashing headlights, these can mean different things, depending on the situation. It can mean: I see you, feel free to drive. It can also mean: what the hell are you doing? Or: you left your laptop on the car roof.
Learning that sort of context is what neural nets are good at. The whole point is that none of this is hardcoded; the AI just learns what humans do in similar situations. At the point they're not even hand-labeling anything. The only input is video.
Flashing headlights can be ambiguous for humans too. There have been plenty of times when someone flashed lights at me and I had no idea why.
Same goes for flashing headlights, these can mean different things, depending on the situation. It can mean: I see you, feel free to drive. It can also mean: what the hell are you doing? Or: you left your laptop on the car roof.