Eric,
Contractive suspension is diferent bird all together. The topout spring is negatively impacts spring prelaod and sets ride ht.. In that sence the function is the same. As for performance, the topout spring can reduce high siding or standing up in some circumstances. Traction cn be improved as the wheels traction is improved as a function of spring preload, and the increased contqact duration. If you invistage we have several string about this allready in this forum. So do some searches under top-out springs, 02 CR's and Works WP componets.
Contractive suspension was used to both spring and damp the bike negatively from what I remmber.
BR,
Jer