Why would generated code be unauditable?

The inputs and the generation will obviously be defined.

That's not the case for autotools output, or flex and bison output.

If the generated files are what you say? Well, just embed the generation step into the build system. A simple approach like that is easily made reproducible, and we avoid introducing noise into the repository.

The blog post do explain why some of the generation is done separately. But yes, that is also a viable approach.