a rolled thread also (very slightly) increases the diameter of the final threaded portion compared to the original diameter of the stock (in this case a tube) since the process forces metal both UP (in the tread crests) and DOWN (in the thread roots). Not sure if that small difference would require slightly undersized steerer tubes (or lathe-turning them down) or if that could make crown fitting a problem and in either case if that could be a deal-killer.