No, it doesn't give aileron function on the rudder (left) stick. It gives rudder on the rudder stick. You plug the rudder in where it is supposed to go, in the rudder port on the rx. That part of it is the same as any other plane.

What makes it work is the AIL-RUD coupling, which affects the right stick. The reason the function is there on the radio is that sometimes people want the rudder to assist the ailerons automatically when they move the aileron stick. It can help overcome adverse yaw, which is caused by aileron movement. I use it on some scale models. The radio allows you to select how much coupling you want. On a WWI bipe, for instance, I will generally use about 20%. When you move the aileron stick, the ailerons move normally, but you can see the rudder move a little too. That is the 20% coupling.

But for a two or three channel plane, with no ailerons, I choose the coupling function and set it to 100%. Now when you move the aileron stick, instead of the rudder moving a little, it moves exactly the way it does from the rudder stick. Since you have no ailerons in this case, moving the rudder is all it does. So now you have identical rudder control from both the left AND the right stick.

Make sense now?

Jim