https://www.osnews.com/story/141633/apples-macos-unix-certif...
EDIT: And really, UNIX certification means nothing except to potentially government agencies and people who don't understand what UNIX and/or UNIX certification is. Or why being "certified UNIX" is generally meaningless: see the BSDs, which are much closer to "UNIX" origins than macOS will ever be.
Or Windows, which is frankly just has better architected internals and abandons legacy UNIX ;-)