I really don't know. This is spitballing, but I think maybe physicists are clever analysts while CS people are prone to "clever" implementations.

I remember thinking "oh, you understand, like actually understand" to them in particular, so maybe it's that they spend more time understanding before doing.

"ex-army programmers really excel in their junior years"

My feeling is that they're just built different, military, especially in US will either teach you or make you disciplined (not something I'd say about my country, you'll learn how to get hazed and drink). If you have a task, well, you better solve it quick, no distractions.