I too was infantry. And muscle memory doesn’t necessarily mean always being engaged to the process, it means being able to return to the necessary posture when needed.
It wasn’t uncommon for us to rest our hands on our rifles too when we didn’t need to be actively engaged in the current situation in any hostile fashion.
Systemic racism in the US ment an inproportionate number of drafted service personnel were black as white draftees were able to get college deferments in higher numbers.
This boiled back down to the poorer economic situation of black peoples in the Civil rights era fighting for basic equality.
The draft also caused friction that increased fraggings as this racist treatment by educated white officers or NCOs were dealt with locally. Fragging was furthered by a disconnect between draftees who wanted to just survive and glory hounds who saw military service and War as some great adventure.