No, not trolling, just expressing an opinion. Sorry if you find my opinion disagreeable.
I suppose it depends on what one means by OS. Toy OSes get built all the time. "Full featured" OSes are built rather less often: it was not at all clear to me that TempleOS fit into the latter category, and, from the video, it looked more like the former.
I dont particularly care about convincing you of that nutjob's brilliance. Perhaps you would care to convince me that, I don't know, erm... goats prefer chocolate to, uh... pantyhose? As long as we are on the topic of things I could care less about....
And sorry, not trained in CS, although I have heard more than enough CS undergrads, and post-grads talking about their FS, OS and compiler writing projects to feel quite comfortable with my assertion.