Hmm, I was looking at the extended keyboard layouts previously had doubled Windows keys; that's a pretty clear spot to put it there. Looks like a lot of laptops don't have the doubled-Windows keys?
Depending on the size of the keyboard and on the size of your hands, using the left modifier for that shortcut might need two hands instead of just one; it's very convenient to be able to quickly lock the desktop with only one hand.
I just tested and,on a full size model m, I can still stretch 2.5 inches after reaching the left+win from my pinkie and l with my thumb. And I have average hand span for a man.