In my experience there is exactly 0 correlation between certification needed and code Quality. Right now working in a multi billion company doing SW that must pass many certifications. The code is absolut trash. The tooling is terrible. The people confuse make and cmake. All said. And the SW gets certified, because it is all a matter of how much it costs to certify. It is a kind of high level corruption, that is not seen as corruption.
In my experience there is a correlation. All software I tested that had to be certified had the lowest quality by far. Certification only cared for the happy path and lots of very specific error messages. It was extremely important that the correct error codes were returned in the specified cases. Anything unexpected like e.g. an out-of-memory-error was more or less ignored because the specification didn't consider such kind of error. Even if it made the software unusable - all that mattered was the certification.
