It's just the opposite. It's called a cheek weld. If you don't press your cheek against the stock before firing a high powered rifle, the recoil may slam the stock against your face and give you a shiner. It also steady's your head. Someone coached 0banana how to do it properly. I learned that the hard way at the range in basic training firing my M1 Garand a long time ago (Army range NCOs used to take delite in leaving out that little detail in their training until we fired the first clip of ammo).
To illustrate, go to 5:50 on the following video for illustration: http://www.youtube.com/watch?v=L2rMoSfMlcE
The stock of the M1 is shorter than the shotgun 0banana is firing, so the guy in the vid is welding his thumb to his cheek.