Well I'd guess that if the ailerons or the rudder lock up in flight, they can only lock up in the position they're in at the time.
Isn't it much more likely that they would simply stop responding to control input but still be free to move rather than "lock up"
assuming that they were either cable or pushrod controlled then they would work right up untill the cable finally broke or a loose bolt fell out at which point they would be likely to be free to move.
The control column doesn't just move the control surfaces it also holds them where you want them.
So how could you continue to fly with freely flaping control surfaces?
Would the control surfaces "castor" with the airflow like the steering wheels of a car when being towed? therefoer making it possible to control the aircraft?
Much better brains than mine needed to answer this methinks.