To be fair, maybe your grandpas/uncles simply did better at dealing with it than others did.
Idk if you want to call it PTSD or something else - and admittedly I’ve never served so I have no way of knowing personally…it just doesn’t seem possible to fight in a war, see friends of yours die next to you, and NOT have it affect you somehow. Whether that always rises to the level of what we call PTSD I don’t know; and like I said, some people are simply able to handle those issues better than others.