I have never bought that Marshall stuff, it didn't make sense, and just wasn't credible, nor did it fit countless battles or human nature.
When I was in high school, I spent part of a summer living with MG HWO Kinnard’s family at Ft. Benning. SLA Marshall was a house guest during that summer and I got an opportunity to meet him and to talk with him about his books and about his combat interview techniques. I later used his techniques in Vietnam and found them quite useful, especially in identifying soldiers who were deserving of valor awards.
But, my combat experiences were very much at odds with his Men Against Fire book and the discussions that I had with him. I chalked it up to our improved training, especially TrainFire and Quick Fire (BB guns). I also knew Roger Spiller, who is the guy who really figured out that Marshall’s data was mostly made up.
My own experience was that even carrying 300 rounds per man, much more than was carried by most WWII infantrymen (they had heavier ammunition), our concern very early in every gunfight was ammo resupply, or at least redistribution. No one was shy about firing their weapon, and although seeing enemy soldiers was somewhat rare, when we did catch them in the open, they paid the price.