I think they are misleading with "virtual server" in their advertising, because they also have a service called "virtual dedicated server", which seems to be the real vserver. So, yes, maybe for there "virtual server" they are using a virtualiziation where your Linux environment is provided by their physical machine or virtualization solution, not by your own virtual "disk". If you were not able to choose your operating system when you initially ordered the server, it's probably not a fully qualified virtual server. Have you seen what others like cloud.hetzner.de offer? They are real virtual environments where you are free to install the operating system of your choice in the release state of your choice. It might be a better solution, else you'll always depend on the mercy of your provider.