All I know is what he said.

"what a dummy he was for believing us" -- I don't know if that's really what they thought. Maybe it was more like "he didn't try to verify anything, ask any hard questions, or get any context on it." It's been too long since I've read the book.

Did you like the bit about him telling the Marines, "I want to be a close air support pilot in 'Nam!"

And they said, "No, you're going to be a computer programmer!"

It goes counter to the folklore that they ignore your background and just hand you a rifle.

I've heard the story of new recruits and their assignments told a few different ways over the years. My grandfather credited his ability to touch type with keeping him out of combat, and it's certainly possible that whoever made that decision also noticed a few other qualities that made him suitable for working in an office. On the other hand, I know a guy who was drafted in the Vietnam era after getting a BS in Physics and Astronomy and the Army's best use for him was... combat.

I don't even know the name of the position of the guy who decides where draftees are sent after basic training, but I expect that as with so many other things, some of them are a lot better at their jobs than others. And perhaps the Marines do a better job of it than the Army.