Circumcision affects only the outer skin which is separate from the penis structure.
A tight circumcision does not afect the penis structure or erectile tissues. But as the penis grows, once the skin has stretched all it could, it will pull the scrotum and some pelvic skin up on shaft because the erection will force it up.
Over time, the skin will stretch so that it is comfortable during the erection. (for instance, if you have an adult tight circ, or of you had a tight circ as baby and your penis grows during puberty).
PE works on both the skin and the penis. But the skin will respond to the stretching stimuli much more than the penis, so in essence, PE is a bit like foreskin restoration.