Why is this stated as though it's some de facto software law? The argument is not whether it's possible to waterfall a massive software system. It clearly is possible, but the failure ratios have historically been sufficiently uncomfortable to give rise to entirely different (and evidently more successful) project development philosophies, especially when promoters were more sensitive to the massive sums involved (which in my opinion also helps explains why so many wasteful government examples). The lean startup did not appear in a vacuum. Do things that don't scale did not become a motto in these parts without reason. In case some are still confused about the historical purpose of these benign sounding advices, no, they weren't originally addressed at entrepreneurs aiming to run "lifestyle" businesses.