But that’s not the difference. Any single process can run in a container without much issue. I think volume storage isn’t a solved issue yet, but it is better.
But running a database in K8s is implying (and it’s how the article sets it up) as a cluster. This is a big difference from running a solo instance on bare metal, in a VM, or in a container. That’s the point I was making to the parent comment.
To go up a level (comment), running Postgres in K8s doesn’t really get you much that you can’t also get from a VM (I’m thinking mainly about migration and setup). After that, the benefits come from running a cluster, which K8s can make easier to orchestrate over bare metal. But that’s a different architecture entirely.
Sure, and containers are just plain processes on a VM. The exact code that controls processes in a VM, also controls processes inside a container.
As long as the underlying data volume is reliable, it really doesn't matter whether you're running it outside of a container or not. Volumes for K8s have a come a long way since its early days.