Having seen and treated many keloids this size, I can tell you there is absolutely no correlation between the severity of the injury and the size of the subsequent keloid. I have seen keloids this size start from an ear piercing or a pimple. Likewise, they often will recur larger than the original keloid after an attempt at removal. While they are a benign overgrowth of fibroblastic scar tissue in susceptible individuals, they are often unsightly and sometimes are painful and itch. The most successful treatment is surgical removal followed by immediate low dose radiation.
In this case the scalp injury could have been quite severe, or may have been a bandaid shrapnel wound like Kerry sustained. We will not know without his medical records.
Well doc, the wound was severe enough to have kept him away from duty for at least a month. Is skin grafting ruled out here to replace missing scalp?
Earlobe keloid after piercing