How on earth can that work? I'm not saying that stiffer springs don't have other advantages (& disadvantages), but if you are getting clutch creep it is because there is drag between the driven & the friction plates.
By some means the plates are pushed apart.
This will take the form of a shaft moving a set distance stopping the force of the springs acting on the pressure plate.
The problem of creeping occurs when that set distance isn't enough to overcome the drag from sticky oil, warped plates taking up more space or most likely plates hanging up on ridges on the inner or outer basket.
Can also be if the set distance is from a spongy or ridged arrangement. Bad hydralic fluid or system, poor cable if applicable in lesser bikes, or pushrod/lever doofer.