Sorry, I should have been more clear. Independent validation and verification is a thing: https://csrc.nist.gov/glossary/term/independent_verification.... We still use it in, for instance, NPP automation, avionics, and defense. Which not only makes sense but usually required by law. Interestingly, outside these few domains, we usually omit it as too costly as if doing the first and only independent validation with our own users is not.