Respectfully, that's nonsense. Linux is directly inspired by Unix (note: lowercase) and Minix, shares many of their traits (process and user model, system calls, shells, filesystem, small tools that do "one thing well", etc.), and closely follows the POSIX standard. The fact that it's not a direct descendant of commercial Unices is irrelevant.
In fact, what you're saying here contradicts that Rob Pike quote you agree with, since Linux is from the 1990s.
But all of this is irrelevant to the main topic, which is whether systemd should be part of a project that teaches the fundamentals of GNU/Linux. I'll reiterate that it's only a distraction to this goal.
So is UNIX design only great when it serves the message?
If you're going to argue that Linux implementing systemd is a good idea because it's following the trend in "proper" UNIX descendants, then the same argument can be made for it following the trend of BSD-style init systems. It ultimately boils down to which direction you think is better. I'm of the opinion that simple init systems, of which there are plenty to choose from, are a better fit for the Linux ecosystem than a suite of tightly coupled components that take over the entire system. If we disagree on that, then we'll never be on the same page.