Originally Posted by oldschoolbike

At least one of the gears of a normal freewheeling AW three-speed hub works by over-running a directional clutch (you can hear the pawls as you pedal), so there is some directionality in the planetary gear set. It's hard to imagine that that would function as a fixed gear, so maybe the fixed 3-speed hub had a different implementation that eliminated any directioanality.