That's an interesting point, but I think it's fair to say that usually when you're talking about a desktop computer you mean a computer whose interface is on your desk, similarly to how a laptop relates to a lap.

For what it's worth, I find the desktop metaphor in UX design a pretty tiring historical artefact. A desk, as a workstation, is the way it is because of physics. Computationally driven user interfaces don't have those constraints and it's awkward, not to mention short-sighted, at least in my opinion, to force one upon the other.