@thomholwerda It's reasonable to assume that Apple's Unix certification is primarily meant to fulfill requirements for procurement rules. See also what Microsoft did to comply with FIPS 151-2 back in the day with the Windows NT POSIX subsystem.

The macOS certification is for UNIX 03 and only for that. I doubt that in practice anybody cares all that much about a standard that is well over 20 years old, which presumably was kind of your point anyway.