ummm... that is the same threadless system that has been used on most production bikes for the past decade. The top cap sets the bearing preload and the pinch bolts on the stem hold it tight to the steerer. Yes, you can change the height of the stem by moving the spacers over the stem, but the only way to shorten the steerer would be to cut it. Actually, it is lighter and easier to maintain than a threaded headset with a quill stem.