The topic is about differential (on a Cub), and I indicated that diffy was helpful on a Cub, or most high wing trainers. These planes fly slower, therefore at a higher angle of attack where down aileron creates the most drag.

High performance planes fly at a lesser angle of attack so there is somewhat less yaw coupling. The yaw still exists but not as noticeable. Usually (though not always) pattern planes are flown by those who have learned to use coordinated rudder. Also you would not want diffy if you plan to fly inverted.

The yaw occurs on all wing profiles but it is more pronounced on a flat bottomed trainer. Some high wing trainers have symmetrical airfoils to allow a student to practice some aerobatics including inverted flight. Again, you would probably not want diffy on these planes.

Bottom line...Is diffy absolutely needed? No. Is it helpful? For a beginner, it's a mixed bag. It will help make smoother, more scale like turns, but it should not negate proper use of rudder in turns.

Bob