It's a bad translation, i know.
Here's the gist of it:
He (weighs about 100kg) used to have the standard spring with a lot of pre load.
With the new spring and much less pre load, the suspension reacts better to small bumps and he was able to "load" the spring better for higher jumps.
Also when jumping of higher rocks, the spring doesn't "bottom out".
Because the rear suspension doesn't sag as much, it also improves the handling and gives lighter steering.
Even lighter expert riders can benefit from this heavier spring, because they can load the rear suspension to jump on higher obstacles.