What is the theory of balloon expansion for scalp scarring? (From Reddit)

The concept is simple enough. The normal scalp is stretched slowly over weeks with a balloon placed under the healthy part of the scalp, then inflated three times a week until enough stretch is achieve to be able to advance the normal hair to cover the scarred area which is removed on the same surgical procedure. It is not as painful as it looks. I have had patients wear a soft hat and they disguised the entire distortion. The scarring on this man most likely came from either an accident or a burn.