> However, it's not an up-front design doc, it has clearly been written after the bulk of the work has been done, to explain and justify rolling out a big change.
Huh, I don’t recall reading this paper before, but it’s terrific! I hadn’t previously seen it laid out as clearly as this, but yes, “faking” the design doc is exactly what happens in practice, and it’s a good thing! Since we want design docs that are useful now, not just obsolete historical artifacts.
Shades of Parnas! [0]
[0] 'A Rational Design Process: How and Why to Fake It', Parnas, Clements, https://users.ece.utexas.edu/~perry/education/SE-Intro/fakei...