Yes, learning has an impact (negative and positive) on creativity, but not learning has an impact on your ability to design and implement in general.
In addition, what Unix mistakes do you see in Singularity, for instance? It's drastically different from Unix-like kernels in effectively every way.
What OSes would you recommend that budding OS developers study, if not these? Amoeba is one of the few I can think of off the top of my head that might fit what you're looking for.
Building a demo and building a full kernel are two very, very different things. In addition, it really says nothing about the design, but the implementation (again, we come back to implementation). There's no reason you couldn't implement orthogonal persistence in a Unix-like system, even if it's not optimal.
Honestly, I'm sort of baffled we're still arguing about this. I can't stand Unix-like kernels, I just believe that this particular tutorial is excellent at teaching the basic concepts required to put together any OS. If you find a tutorial of this sort of quality for any other design, submit it and I'll be certain to upvote it.
The world needs more OS designers, and tutorials of this sort lower the barrier to entry.
Edit: Also, if you're on Freenode by any chance, shoot me a PM (my nick is my username here). I always enjoy talking with someone who's as passionate about OS technology as I am.
In addition, what Unix mistakes do you see in Singularity, for instance? It's drastically different from Unix-like kernels in effectively every way.
What OSes would you recommend that budding OS developers study, if not these? Amoeba is one of the few I can think of off the top of my head that might fit what you're looking for.