Unknown device as well. T-Mobile's little phone identifier is wonky, though. When I had my Nexus 4, it was first displayed as such but later changed to something weird (I don't recall what, but something like "Used Android Device."
I wonder if (and suspect) it's because this is a BYOD phone. Whenever I go into a T-Mobile store and tell them I'm using a Moto X, I get some rather confused looks!
When I switched to the Moto X I think I selected my device is not listed or something like that. For some reason it switched back to my old Optimus L9 so I had to reselect not listed.