No. I can say this with confidence because I am an expert on war crimes - I have consumed two, maybe even three distinct pieces of media where war crimes have been mentioned. At one point I even glanced at the Wikipedia article on war crimes. You can count on me.
For real though I think throwing a frag grenade into an enemy army's bunker can't possibly be a war crime. The deception with the tin cans isn't relevant.
Double edged sword. Applications asking if you want to save your stuff aren't designed to annoy you, they're designed to save you from the headache of losing your work.
But I can see why you'd want the power button to be a "stronger signal" than clicking Shut Down in some menu.