Kubernetes is optional - Docker Swarm (which some people prefer for its simplicity is also available) - basically yes binaries get wrapped in containers now for build/ship/run.

You're right though it is just an example - one of many in the function store. OpenFaaS can run any binary as a function - that means that we can strip back all the complexity needed to utilise ImageMagick for instance as a function by making it a function that works over stdin/stdout. Normally that would have involved a Node.js runtime and native compilation packages.

Here's the example: https://blog.alexellis.io/serverless-imagemagick/