No dispute here, I was just pointing out that OS X not only stems from Unix (as does, say, FreeBSD), but the "is-a" property also stems from the Open Group actu

No dispute here, I was just pointing out that OS X not only stems from Unix (as does, say, FreeBSD), but the "is-a" property also stems from the Open Group actually putting a stamp on it. This isn't to say OS X is "more of a Unix" than FreeBSD. It means simply what is says, without any other implication: the group that is allowed to say "yeah, this is unix" said that about OS X.