Mechanical feature of accelerator pedal on torque delivery: 300 SD

I've noticed a very interesting feature of the accelerator pedal. With the car in drive and at idle, if you apply slight pressure to the pedal it will give about a half centimeter and come to stop position, which can definetly be felt by increased resistance. With the pedal in this position there is no increase in RPM, however, there is definetly more torque going to the wheels, because the car will ever so slightly lunge forward even on a slight incline. The mechanics of this operate so smoothly that I'm sure it must have been designed like that for some reason? Has anyone experienced this little marvel?