The xinetd vs. inetd thing was just an off-the-head example; I don't know that he even specifically said that one. It's just one that I know about from having wrestled with it.

Linux is often described as a "Unix compatible operating system", but that doesn't say much. Which Unix? Even different flavors of "real" Unix differ. I've used BSD, Ultrix, Dynix, HPUX, AIX, and probably some other fillintheblankX's that I don't remember. They all differed in various ways, sometimes significantly.

Yes, Linux isn't Unix. But as a Unix shop (currently mostly HPUX, some AIX), it is better from our perspective for a Linux distribution to be closer to Unix than farther away. That which takes it further away makes it harder to maintain.