Arguing with Brooks about software engineering practice feels sort of like arguing with Knuth about typesetting software.

I'm willing to argue with Brooks and Knuth when they're wrong. :)

I interpret Brooks' comment above as countering the fallacy that you can know ahead of time exactly what you need to build and that you'll design it appropriately without having built it. In that vein, anything you can do to incorporate useful feedback into the coding process will help you produce the software you really need to produce. Remember, writing an operating system in assembly in the 1960s is a little more difficult than writing a business-logic server in Perl in the 2000s.

As for Knuth, I'll paraphrase what Bob Frankston once told me. "You can assume that the cost of memory access is uniform, but it's not."