A lot of this seems to stem from "unit tests slow you down" vs "unit tests make you faster". Unit tests DO slow you down at the start of a project and I'm sure Uncle Bob et al would not argue against this. It will take anyone more time to write fizzbuzz with tests than without it.
It's only when you've brought together enough code or developers or overlapping features or bitrot where tests will start catching undesired changes in behavior. If the authors of the first pass of the Mozilla browser say it would have slowed them down on that initial release, I don't think anyone can credibly argue otherwise if they weren't there. I'll also let the long term stability of that browser speak for itself.
It's only when you've brought together enough code or developers or overlapping features or bitrot where tests will start catching undesired changes in behavior. If the authors of the first pass of the Mozilla browser say it would have slowed them down on that initial release, I don't think anyone can credibly argue otherwise if they weren't there. I'll also let the long term stability of that browser speak for itself.