I think what happens is that with the stretching, the fat and skin aren't connected to the body as firmly as they were pre-Penis Enlargement. My thinking is that the connective ligaments that hold the skin to the layer below the fat get broken from the pulling. This explains how some of us can pull the skin over the glans now when erect even though you don't have enough skin to qualify as a real foreskin. Those ligaments are the same that cause "cellulite" to form when people get too fat.
The same separation happens with foreskin restoration.
The only way to avoid this would be to never pull the skin forward, which is probably impossible to do when doing Penis Enlargement, or foreskin restoration.