If you pull the foreskin back fully so that it is smooth on shaft, you see only the transition from shaft to inner skin which can be "abrupt" or more smooth depending on guy (obviously not as abrupt as on a cut guy). There is no "ridged" band or "preputial sphincter".
If the frenulum is too short, it prevents foreksin from being retracted so it is smooth on shaft, at which pioint you have wrinkles generally where the shaft skin transition to inner skin. (this is what the intactivists calle the ridged band). It is just wrinkles.
The bigger difference is on ventral side because for a cut guty, the frenulum, if still there, is just a line down to the circumcision line and meets with the raphe.
For an uncut, the frenulum starts to spread out as it goes down. For a long enough frenulum, this is less perceptible, for shorter frenulum, it bcomes very obvious because it widens into what becomes the "ridged band" on eiother side of the frenulum.
"Preputial sphincter" are anti circer fantasies. Simply denites a narrower part of fopreskin at the tip which need to stretcy much more when retracted because its "normal" diametre is very small. On a helthy uncut with easlily retractable foreksin, this doesn,t exist, same with an uncut with short forekmsi without anteater overhang since the foreskin, at its furthermost point, is still over glans and thus not at diametre 0.
