It's AWS Outposts Rack without the AWS connection. That is, you get a turnkey rack with the servers, networking, hypervisor, and support software preconfigured. You plug it into power and network and it's ready to run your VMs.

Outposts, too, started with a full-rack configuration only, but they eventually introduced an individual server configuration as well. It'll be interesting to see if Oxide eventually decides to serve the smaller market that doesn't have the scale for whole-rack-at-a-time.