If you try to run the machine with just water with the water level to mini on normal speed, you'll see the water gets so high on the sides of the tub that there isn't enough remaining under the agitator and the pulsator gets out of the water and makes a relatively loud noise when it hits the water on it's way down. Doesn't do exactly the same with clothes in but as Jon said, it's still not recommended to use it with a water level below "Small" on normal speed. In fact, the 1979 WEG "Elite" washer even had a feature that prevented using it on normal agitation speed if the water level selected was set below "Small".