PG already has its own clustering solution to scale up and down, which is orthogonal to Kubernetes. So running PG in Kubernetes does not add anything. Also, you are much more likely to mess them up when trying to mix two orthogonal technologies.
And the DB is not meant to create and recreate often unless you want to purge the data. So my take is this: Kubernetes is to manage and configure microservices and DBs are not microservices.