[ropejumper]

The amount of braking you can apply before flying over the handlebars decreases significantly the more you move the center of gravity forward.

[Toutouxc]

People who can ride shift their entire body back when emergency braking, which is much more significant than some added weight on the front wheel.

People who can't ride usually don't go OTB because of the torque around the front wheel (i.e. the entire bike rotating), they go OTB because they can't handle (or aren't ready for) the sheer force of the deceleration, it makes their hands fold.