I read through this and I don’t feel like the article didn’t tell me anything about K8 Application Operators. I expected something about custom controllers or meta pods that manage other pods, but that wasn’t in the article.
Maybe you have a different view on the role of an application operator? I’ve linked to the definition I’m subscribing to (stemming from Helm) in the first paragraph. What could be the case is that you’re thinking of the term “operator” (roughly: a CRD+custom controller) that CoreOS established. If this is so then indeed, the article has nothing to do with it.;)