alt Hacker NewsThe compliance trope that a point-in-time-assessment can't be used to support a claim is kind of a lazy take. The certification explicitly states macOS v26.0 Tahoe.
While it's true that it wasn't always truly UNIX compliant, they put in the hard yards to become so (albeit to avoid a $200M lawsuit from The Open Group) [1]
[1] https://www.quora.com/What-goes-into-making-an-OS-to-be-Unix...
To certify any version of macOS as UNIX, the security had to be significantly altered (disabling SIP) among a few other things. This is why what is shipped is not what is certified as UNIX. You can /make/ it match what is certified as an administrator, but that would be inadvisable.
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 ;-)