Considering I can run Docker containers, log in, install software manually and then snapshot the images, I'm not sure what I get from this other than a terrible sounding workflow.
LXC is best thought of as a way to make a VM, but each of your VMs shares a kernel and filesystem cache. Each of these "VMs" can have a unique IP address, and even a totally different userland, but is otherwise best thought of (For better or worse, depending on your needs) as a VM / computer on its own.
LXD is an orchestration mechanism to provision / manage these LXC containers -- it's like but not really like nomad or kubernetes.
For stateless things, I tend to use docker / OCI containers; for stateful things I tend to use LXC because the volume mounting abstractions in OCI containers just get in the way.
But that's me. I'm sure I'm doing it wrong in a variety of ways.
I can also put that users home on the SAN so their data is retained if the container has to move servers. I'm unclear what that has to do with being an LXD advantage.
I "can" do what they are describing in OCI, but it's bad practice.
I don't do it manually.