Actually, the handbook that came with my CMP Garand specifically warns NOT to clear a jam that way, saying, with masterful understatement, "that leaves the muzzle too close to your head for safety."
Yes, but the Krinkov manual translated from russian probably reads something like: "If this weapon jams you cannot kill enemy for mother Russia, if you do not kill enemy, they will kill you, if enemy doesn't kill you and you still do not fight, then we kill you. What do you fear more, an accident clearing a jam, or US. Clear the jam with your foot sissy, and we will not kill you."
In a situation where lead is flinging, and your rifle is turned into a club by a jam, a 1/1000 chance of a slamfire in the head is a small price to pay to clear it quickly, compared to going hand to rifle with some marines. In the civilian world, unload, pull back the bolt hard, if this doesnt work, take a shoelace, or peice of rope, fold over the bolt handle, pull it tight and wrap over the buttstock, quickly pull the center of the rope down, and the jam will clear, all with the muzzle under control, downrange. Pulling the dustcover off, putting the rope through under the piston rod and above the bolt, wrap each end in a hand, put the stock in your gut, and have someone hold the rifle, pull briskly. stomping on it works, but can be dangerous, or can get you thrown out of a range, and if it does go off, is shouldn't be pointed at your head anyway, but the bullet will go flying somewhere, OK in battle, definitely not cool at the range