Comment by p_ing

Related:

https://www.osnews.com/story/141633/apples-macos-unix-certif...

Identical changes were made for Tahoe's certification. This includes disabling SIP.

https://www.opengroup.org/csq/repository/noreferences=1&RID=...

So Tahoe is certified, but what ships with every Mac isn't certified UNIX. Not that being certified makes any difference what-so-ever.