My pleasure. Glad to help. And a hug would be nice too. I'm a lumberjack and I'm OK.
So I was a little pressed for time earlier when I posted that diagram and didn't have time to talk about the use of flashing the high beams here in the US.
First of all, if we here were to flash the high beams, we would just pull back on the HI/LO stalk twice in rapid succession. More modern cars have a "make-before-break" type of switch now, but back when the Z's were new, you just pulled the stalk twice. And even before that type of control, the homegrown stuff here often used a foot switch operated by your left foot. You would stomp the switch twice quickly.
As for the meanings... Just like where you are, there are several different meanings to the flash. I don't know if there are regional differences in the USA, but where I come from:
Quick flash at an oncoming driver can mean "I just passed by something that you might like to know about and you should pay attention." Things like debris on the road, animals along the side of the road, police ahead. That sort of thing.
A quick flash at an oncoming driver may also be "You have your high beams on and it bothers me. Please put your low beams on." That may be quickly followed by a longer flash if the desired response is not achieved.
A quick flash at an intersection means "You go ahead. I'll wait."
A flash from behind usually means "Move over, you're driving too slow." The length of the flash is usually commensurate to how frustrated the guy in the rear is.
A quick flash on a multi-lane highway after you have been passed by a faster vehicle means "You are safely beyond me and can tuck back into my lane if you wish." Most often used by trucks, but sometimes I'll give trucks that sign even if I'm driving in a car.