That's pretty much the baseline when dealing
    with any software system

Exactly. And now instead of one system, he has 11.

    All it takes is inheriting the latest
    version of an image

He is not using "an image". From the article: "After the Alpine Linux 3.9.1 release I noticed the official Docker images had not been updated so I built my own."

    I mean, this stuff is handled
    automatically by any CI/CD pipeline.

He has not describe any CI/CD pipeline involved in his infrastructure. Yet another aspect he has to build.

    you can also sh into a container
    and upgrade it yourself

Into all 10 containers.