Tip stands and nose heavy landings are not pre-release... That is an issue of Torque forces, and involves concepts and math I would rather not try to explain. To put it simply, in a tip stand, or nose heavy landing, a stiff ski is producing a much higher force at the binding, causing it to release. BUT it is still releasing at the intended force value. That is not a pre-release.
PRE-RELEASE: is when the binding is functioning normally, and yet due to conditions caused by the ski/skier, releases the boot at a LOWER FORCE than is ordinarily required.
The main cause of pre-release is flexion/deflexion of the ski, such that the forward pressure of the binding is compromised, and the binding fails to operate as intended, releasing the boot at a lower force than normal. This happens much easier in a softer ski, simply because the ski flexes so much that the distance between heel and toe of the binding changes enough to affect the forward pressure, and therefore the performance of the release mechanism of the binding.
By the way... I own lizzies, I ski them often, and I can tell you with great certainty, that at the same DIN value; my Lizzies and EPs prerelease far more often than my Silencers, JP vs Julians, and much more than my Chopsticks ever did. And what do you know?! they are really soft compared to the others.
To Sum Up: Fatter, softer skis prerelease more than stiffer, narrower skis...