extends well in front of the glans, so there is plenty to roll back behind when you retract it. Take a look at this page
(all pictures of the same foreskin as far as we know) to get an idea of this, especially pictures 8
which demonstrate that the frænulum should not
significantly restrict retraction.
It follows then that circumcision is intended to remove that tubular part of the foreskin which would normally pull behind the glans so that the only difference in appearance when retracted would be the amount (and texture) of skin immediately behind the glans.
The frænulum is involved to a varying degree in circumcision, depending on how much it restricts the foreskin being pulled back, since pulling back the foreskin is generally part of the circumcision procedure. It is
common to divide it first in order to pull the foreskin back where the circumcision is performed on the excuse
of a non-retractile foreskin because if the foreskin has never retracted, the frænulum has generally never been stretched (by routine retraction) to its proper length. Where a circumcision is performed for cosmetic perversion (on a fully functional penis); the frænulum may not be involved at all.