This is a stupid article. You need Linux to run Kubernetes, one (and the way it's configured is even more important given the thinner security barrier between containers and their host), and, two, not every workload will be suitable for containers or Kubernetes.
Guessing my OS, they mean just like back when the web was taking over and the web was the os, taking over from Windows. In this case, you don't build specifically for Linux, but for Kubernetes and it can be deployed anywhere, including Windows, eventually.