Why are software companies still grappling with the mythical man month? You'd think by now we'd have learned our lesson. More hands /= more productivity, at least on a linear scale
If you're talking about Brooks's law, that's a pretty specific observation that doesn't seem like it applies here. It's very specifically about adding workers to a project that is already behind schedule. It doesn't certainly doesn't mean anything as broad as "a company cannot do more things by increasing its employee count."
I don't think I've ever worked on or even seen a software project that wasn't in some way considered behind schedule. Very, VERY rarely are the correct number of people hired at the beginning.