Here in France, if I ask for something during the interview process with the recruiter, I will get a response like this: "Sorry we don't do that in our process, so goodbye" and they move to the next candidate while I'm out for this job.
Eastern Europe, the same. I asked a couple of years ago what are the credentials of the business unit manager, of the line manager and the technical team lead. They almost laughed me away from the building.
I'm sure plenty would explain their processes and how they code, but they're not showing you their code unless it's already public which would be a moot point then.
To see some code is definitely out of the question, though. But asking about the development process et all I find to be the type of mandatory questions I would ask as a candidate (and expect to be asked as an interviewer) even if I already knew the answer, just because not doing it would be strange.