Harry,

A lot of these pattern people think they do that. I think what they're really doing, possibly without being consciously aware of it, is crabbing, and entering the crab by making a skidding turn, which makes the judges happy because the plane doesn't bank. They may even be keeping the plane cross-controlled all the way along. Sort of a Chinese pass, but with the wrong wing down, and then a crab the other way to keep the sideslip from taking them off line. Either that or they aren't really "holding" rudder, they are just using enough rudder to keep the plane where they want it to be (which turns out to be none, but with your mind on other things they may not notice that).

There may be some pattern fliers who are also full-scale pilots, but I've never met one. No full-scale pilot could possibly believe that holding rudder can either cause you to yaw or keep you going straight, depending on what you want it to do.