I don't think he's specifically referring to POSIX compliance in the current OSX, but I can certainly attest to my experiences with A/UX (the original Mac OS/Unix hybrid OS) and say that POSIX compliance was also a minor issue - perhaps not so much for a Unix, but it's other stuff that they let slip. I don't use OSX as I don't have a Mac but I wouldn't be surprised if they're focusing on the insanely great bits to the detriment of stuff under the hood, as has happened before.
