A great reflection on a master of the streets... How he managed this with a Leica's viewfinder so far from the taking lens I shall never know. Apart from a very early one which I had where the viewfinder was just above the 50 mm lens I have always been in a panic with later M series cameras with viewfinders far off on a diagonal. Killed all spontaneity for me.
Hmmm,I just compose within the framelines for the lens on the camera...it does take some getting used to, though. I prefer the 35mm lens on my M4, but occasionally I will use my 50mm...the M4 is a joy to use! https://inside.cias.rit.edu/wordpress/wp-content/uploads/2014/10/Leica-M4.pdf