Not only can you leak pre-cum, you can orgasm and shoot a full load without an erection. Maybe not when you are young, but later in life.
I've had the opposite experience. When I was young, high school age, and long before I had a girlfriend, for some reason I usually masturbated without an erection. I had to mentally prepare myself beforehand, not let things escalate into an erection, or when it did, then stop and wait. I don't know how it started, but that was just the way I did things, probably from never talking about these things with friends or classmates and certainly never doing this with anyone else.
In any case, the result was a very inward experience, with orgasm seemingly radiating inwards instead of the typical outward gushing feeling of an erect orgasm which becomes concentrated on the penis alone and much less on other parts of the body. These kind of orgasms were very intense and from what I've read seem to be as others describe anal orgasms to be.
Now it's just the opposite as a non/semi-erect orgasm requires quite a bit of effort physically. Yes, I know this sounds counter-intuitive, but believe me, the strain on the heart is quite marked.