This article starts with mediocrity, but continues with confidence, and a story of actually avoiding mediocrity. Of course one can beat the average or mean or median with the growth mindset! And the growth mindset is easier to acquire being mediocre than when gifted.
And especially boys usually try to be the best in something. It becomes less important when you actually are.
Surprising conclusion may be, that only society as a whole benefits from mediocrity, it's more stable that way.
Does being mediocre give advantages, comparative or not, and makes one more successful? I do not think so. Raising confident kids may be an exception, but then again one needs to be better than average father. SO lets say I am not convinced by the main statement of this article, though I can related to the story.