Yeah, from the looks of the episode count, I think NBC must have ordered a full, 22-episode season (otherwise there'd only be 13 episodes), and then changed their mind and decided not to produce the whole back nine. I absolutely LOATHE it when that happens, but fortunately, not counting shows effected by the strike, the last show that I watched that had that happen was ABC's "Complete Savages".
But seriously, if a network orders the full season, they should at least have the decency to let the full season be produced, and just inform the producers they won't be back for another year. Then those final few episodes could be used to provide some sense of closure.