> The miss is that the article in the link doesn't discuss VMs or virtualization at all, so talking about oversubscription/etc seemed like an ad-hoc commentary on the hardware configuration unless I totally missed that in the article

There is a giant table in the middle of the article that is impossible to miss if you read it. It literally says # of VMs. As well as calling out VMware, and z/VM as tye hypervisors in use. The oversubscription is a simple math problem, and that's assuming best case scenario.