I believe that as you steer the bike, the top race will want to unthread itself. It always does, that's why the top nut has to be so tight to keep everything in place. The finely threaded upper race has a mechanical advantage over the devices that try to keep it from backing off. The equally fine threaded top can do the job but I don't think the stem clamp can stay tight enough to do it. I doubt you will have any kind of catastrophic failure but you will find yourself tightening everything down very often. Possibly after every ride. I admit this is only a guess since I haven't tried this so let us know how it turns out.