They lost power - putting them in a drift, power comes on, smoke goes out as they slam full astern (roll coal) but that doesn't provide steering.
Yes - full astern means full reverse. The prop spins the other direction but doing so doesn't push any water over the rudder for steering. The spinning prop then spins the stern of the boat to port because of it's spin direction.
A twin screw boat can steer in reverse because one engine in reverse, one is forward - causing a pivot like a tank and one side IS pushing water over a rudder for control.
