Tracking back is part of the job, I listed other examples. And yes, tracking back is part of defending (not all of it obviously). There are some very basic elements of defending you can ask your attackers /wingers to do that make the world difference for your defense. Movements, understanding and intercepting passing lanes, understanding where the defenders are or will be moving so you know what space you need to occupy to support them.
And yes Mr. Obvious, there are glaring differences between the players you mentioned. What's your point? They collectively help out (some more than others) defensively when necessary.