Even a lower stack headset wouldn't make much of a difference, maybe a 1cm at most, and even that doesn't bring me into the light. I would bet that it was either cut down or from another bike.

Oddly enough, at the co-op there was another fork, identical to mine, but with less steer tube and also threaded. What I take away from that is that there are a lot of these gray rockhoppers around.