When I was in, we would derogatorily be called “John Wayne” if our chin-straps weren’t connected.
I remember seeing a wall with a cargo net but I don’t remember going over the side.
But maybe Marines climbing down a cargo net were supposed to have their chin straps undone as shown in this video.
https://www.youtube.com/watch?v=zszJ5_u-9P0
Interesting question. I am not sure. My husband noticed that while they were running and shooting, etc. They were not strapping their chin straps on. I could see how that could be a distraction.