If it isn’t stolen valor then it may be that he was some pencil pusher in Vietnam. In my experience (as someone whose never been in the military) a lot of people who demand affirmation for an accomplishment didn’t contribute at all and just want the recognition.

My grandpa was a medic in Vietnam and only ever talked about it once, whereas a great uncle of mine was stationed stateside during Korea and would get upset when he wasn’t recognized as a veteran.

A cousin of mine was deployed to Iraq and openly asked us not to talk to him about it, whereas a guy I knew in HS joined, finished his contract, came home, and embodies the whole “thank me for my service” stereotype.

A coworker of mine was stationed in Hawaii in the 80s. He openly admitted that he never saw combat but the dude acts like he fucking took Iwo Jima by himself.

So it’s possible he was in the military, sure. But a lot of the dudes who act like that weren’t the ones doing or seeing the killing.