My points though are

1) the development isn't actually using red/green TDD, and

2) the result doesn't show "really good results", including not following a very well-defined specification

so doesn't work as a concrete example of your description of what the second chapter is supposed to be about.

Perhaps you could show the process of refining it more, so it actually is spec compliant and tests all the implemented features?

What's the outcome difference between this approach vs. something which isn't TDD, likes test-after with full branch coverage or mutation testing? Those at least are more automatable than manual inspection, so a better fit to agentic coding, yes?

(Of course regular branch coverage doesn't test all the regexp branches, which makes regexp use tricky to test.)