Funny how different people see things differently. I’m long retired so most of my driving is done in a car. I’ve always flashed lorry drivers in no matter what I’m driving, when I started driving with the roads and the lorries of the day lorry drivers needed all the help they could get and appreciated it. Nowadays I still do it out of habit, they often don’t respond and then move over when they’re ready. Do I get upset? No. I assume they’re not expecting a flash from a car and so not watching the mirror or maybe don’t trust me even if they are.
I don’t give a toss one way or the other.
Bernard