I don't understand this idea at all. Everything POSIX exists inside the the kubernetes containers, so it should be thought as a layer on top, not a replacement. I don't think anyone thinks that kubernetes abstractions replace concepts like files, processes or threads like in the diagram presented.
Hey, I wrote the post. Agree completely with your comments. I was trying to draw an analogy between the two, not imply that one replaces the other
Unix scales complexity. Kubernetes is unnecessary complexity.