More of an Op-Ed, than a true study.
Comparing military open sighted rifles and the style of the day to the “modern” technique and rifles is hardly a
truly valid comparison.
The mechanics of sling location and it’s effect on accuracy, let alone what the rest is comprised of (how soft), the rifle barrel itself heating up and shifting, etc., all play into the question and answer.
Without an in-depth study, same rifle, same rests, different shooters, slings, etc., etc., it’s hardly worth having an opinion yet.