The "Objects in the mirror may appear closer than they are" warning is a US thing also isn't it?
Which one is actually true? Surely if objects are further away than they appear, it's pointless to note that since it's safe. So it has to be "Objects in the mirror may be closer than they appear" right?
If you think about it, it is a concave mirror giving wider field of vision. Concave mirrors give virtual smaller images.
Much along the same idea, coming out of the Ferry Building in San Francisco a few days back when it was pouring with rain, someone had helpfully put out cones to warn me that I was entering the outside and that it was wet. The black sky, and cats and dogs falling from it might have also tipped me off, but thankfully I had the cones as confirmation :)