On the other hand, the racer cherishes the extra boost around every gate. Another kind of stiffness is torsional stiffness. This is the ski's resistance to being twisted. When you're trying to carve a turn the forces will try to twist your ski to avoid setting the edge against hard snow. If you have little torsional rigidity the edge will twist away and your ski will chatter.
Torsional stiffness is achieved by the way the ski is constructed.
I remember having a pair of skinny skis about 20 years ago with low-density foam cores. I could twist them in my hands. I chattered like I was side slipping down a wash board road. I don't think anyone makes tele skis with low density injected foam today. Most skis achieve varying amounts of torsional stiffness by torsion box construction.