This is most often seen in abdominal surgery. Any surgeon will tell you it is much easier to perform surgery in an area that has never been operated on in the past. This is due to adhesion formation that occurs at the site of healing. It is also true for burn victims. As the skin begins to heal, the adhesions in areas of joints can significantly decrease the range of motion.
Circumcision is no different.
The foreskin surrounds the penis and has a natural but superficial attachment to the penis. This procedure involves first separating the foreskin from the penis and then making a circular incision to remove it. This circular edge will tend to stick to the penis as it heals. Full healing takes about two weeks, so if adhesions to the penis are going to develop, they usually do so within this time. These adhesions can be prevented with a simple painless maneuver performed at home.