The summary is that Marshall seems to have made up the statistics about the Malkin Island fight: he didn't have time to do the number of interviews he claimed, soldiers had to be told to hold their fire when they were blazing away at enemies that weren't there (rumor), and it isn't clear if he drew any distinction between soldiers in reserve and those at the point. It took delving into archives and a number of interviews to find this out--not the sort of thing an armchair analyst can take on.
What's really annoying is to find out that he'd been known to be full of it since 1989! But the numbers still circulate. I suppose that's nothing new for made-up numbers, but usually those keep zombie-ing around because somebody has a political agenda or iron rice bowl they need to protect.
Grossman relied on Marshall's numbers, but tried to supplement them with other estimates, so I'm not sure his conclusions are seriously undercut, such as "It is a lot easier to kill a fleeing enemy." Hat tip to West Hunter