The rider leans forward to accelerate the OneWheel, so they are not "actively balancing" - the OneWheel self-balances "against" their lean. Until the motor gives out, that is.
Simply carving , which is how you turn, requires some balancing by the rider. Going fast over anything but ideal terrain also requires active balancing. If you ride one in any capacity beyond a few mph in a parking lot, you’ll feel it in your legs.