...but the distinction should be maintained.
Why? How "unixy" Linux or MacOS is is a really rather tired argument by now, isn't? Having cut my unix teeth on Solaris, AIX, and HP-UX, seems like I should be able to tell how "unixy" something is. I have MacOS because of my work, but I hate it. It doesn't really fee like unix to me at all, and I have a hard time understanding how "unixy" it really is since the kernel is a heavily modified mach clone. But whatever, just saying your reasoning on how "unixy" Mac is seems a bit strained to me, even with a big web page with small characters explaining how "unixy" it is.
The point of my post was more to correct the semantics in the discussion than to debate how unixy either OS is. Mac, Linux, *BSD, and Solaris are all sufficiently unixy for me. But I'm not a real neckbeard--I never used AIX or HP-UX.
By "the distinction should be maintained" I meant the distinction between OS and GUI. Why not? GUIs are interchangeable and optional. I do the vast majority of my work in terminal, my cross-platform text editor, and a browser. I care a lot more about how the OS handles path resolution, variables, ssh, port forwarding over ssh, symlinks, shell expansion, regex, etc. than crap like launchctl or X. Is there even a POSIX standard or anything similar regarding windowing systems?
I'd agree that Mac doesn't "feel" Unixy. But in my experience, it implements the standard reliably enough. I'm curious where it falls short for you (aside from personal dislike, which I totally get).
If you haven't read the standards, you might want to glance at IEEE Std 1003.1, 2013.