That spoiler is there because the corporate attorneys wanted it there. They were concerned about the car being unstable due to some lift at speed from the shape of the rear deck. The lift probably doesn't get real bad until the car gets over 60mph, but the powers-that-be probably erred on the side of caution when they decided that 60mph would be the 'trigger' point, and 39mph was the 'retract' point.

I highly doubt that the trigger points in the computer can be reset, again due to corporate liability concerns.

I'm just glad I can have the thing stowed most of the time, until I get on the highway. It's actually not my favorite feature on the car...