Which is how some of the 'false accident' claim scammers work -flash a car to let them out, drive into it & then blame the 'flashed' driver for the accident. Witnesses in the scammer's car confirm the car pulled out in front of their driver.
I never let cars out unless I have come to a complete stop & then I use a hand gesture to beckon the driver out. Can't remember the last time I flashed the headlamps on my car.
Not every flash of headlamps mean 'out you come'. On a driving course I attended we were invited to write on a white board what flashed headlamps could mean - over 20 suggestions.