Maybe the confusion comes from conflating unit testing with TDD. Different but related concepts. If you write a unit test after the code, that is no longer TDD.

TDD is a major change in coding style and doesn't seem to work for a lot of people, including myself. Unit testing, on the other hand, is absolutely essential and fundamental to the task of building large, complex systems.

I haven't read Coders at Work, but if the guys in there are doing their thing without some kind of automated testing, I would be very surprised, and I'd wonder why they're making it so hard on themselves.