Washout can be used on any wing to help control tip stalling. Many things enter into the manner in which a wing stalls. The leading edge shape can be wrong or different along the length of the wing due to novice builders, the covering sag in the wing doesn't help and then there's just the issue that some pilots figure they can do anything they want by just cranking the sticks and the model should follow like an obiedient computer mouse pointer.

Which all goes to say that there's not right or wrong about using washout but it can be a good thing on any trainer model.