Yes, if you break down each grade, there are individual good and bad grades.
However, in the example, the big picture is the one who just simply chooses the "average" all the time, in the long run, is the winner because he/she is satisfied with effortlessly just doing average again and again, not better or worse than the entire class no matter what without the effort/risk of being a "winner" or "loser."
By just picking the average each time is like doing what the entire class does without having to study. Not a bad deal.
Have you ever seen a headstone with these words
"If only I had spent more time at work" ... from "Busy Man" sung by Billy Ray Cyrus