That's because their penis is always extended in that device (
Phallosan forte) for many hours. If you use something like the
lengthmaster version 3, you only have your penis extended and stretched with that device for 1 hour per day.
You want elongation of your penis more then 1 hour per day, to make it heal longer, and so it will stay more elongated and not turtle/shrink into your body so much.
All the information is in the
SRT.