I would say my foreskin is fairly short and very loose.
I started retracting intermittently around puberty, so I suspect my foreskin didn’t grow quite as long as it might have if it had been left fully forward all the time.
After retracting for so many years, and for such long stretches of time, I think my frenar band has spent so much time around my shaft instead of in front of my glans that the tissues and sphincter muscles are completely stretched out. The tip of my foreskin has very little tendency to pinch together, pulling the foreskin forward on the glans, as it does in many men who usually wear their foreskin forward.
And finally, I pulled and stretched on my frenulum so hard in my youth that I got some small tears that allowed it to heal in a bit longer configuration that puts less tension on my foreskin. Unlike some guys on this forum, my frenulum alteration was entirely accidental, but I think it has contributed to my current success.
If I were to pull my skin forward, it would naturally cover about 1/3 to 1/2 of my glans, a bit more if I’m sitting down or very flaccid, and when I’m erect, it will naturally retract behind the glans.
I think there is just enough constriction at the frenar band to hold the foreskin behind the glans when retracted, and there isn’t so much shaft skin to push it forward over the corona most of the time, nor a short enough frenulum to pull it up over the corona. So I think a confluence of some anatomic luck and some changes from my consistent retraction have helped me reach my current state.