Yes, I do. I recall they had ads where they showed the amazing things you could do with one-line commands at the shell - they had examples of pipelines including grep and awk etc. I remember being amused that these familiar idioms that had been used in the Unix/Linux world for ages were being presented as amazing new capabilities.
What I found amusing at the time was, after years of touting the Mac point-and-click interface as a great improvement over the old-fashioned hard-to-learn obscure command line, they switched to touting the unprecedented power and versatility of ... the command line!
Yes, they got it certified with 10.5, I think. Small market these days, although I'm always surprised when I hear that both AIX and HP-UX are still receiving updates...
It worked on me! I bought a PowerBook G4 in 2003, when I heard Fink/MacPorts and Jaguar were no longer complete nightmares to use. Been Mac only since then.
There used to be things like this on Apple's website, too: https://www.apple.com/media/us/osx/2012/docs/OSX_for_UNIX_Us...
I can't find any mention of UNIX in Big Sur's pages, even though it is listed as certified on the Open Group's website.