Oh please. That's like citing the dictionary definition of a word which has come to mean something else.
The actual uses of flashing headlights are much more varied than the official version. For example "you are driving with your headlights off and it's dark", "you are blinding me with your main beams" and "a tree has fallen in the road ahead". I would wager that the unofficial version outweighs the official 10 to 1.
The only danger with flashing someone to give way is when there is potential for it to cause a conflict with other vehicles, for example a cyclist on your left. For that reason I always check my mirrors and slow to allow someone to cross in front of me rather than flashing them. Most people figure it out but don't completely disengage their own perception.
The actual uses of flashing headlights are much more varied than the official version. For example "you are driving with your headlights off and it's dark", "you are blinding me with your main beams" and "a tree has fallen in the road ahead". I would wager that the unofficial version outweighs the official 10 to 1.
The only danger with flashing someone to give way is when there is potential for it to cause a conflict with other vehicles, for example a cyclist on your left. For that reason I always check my mirrors and slow to allow someone to cross in front of me rather than flashing them. Most people figure it out but don't completely disengage their own perception.