are you trying to justify removing the shellac and applying BLO or poly?
My take on it... the shellac was there to be the final finish, but being typical russian workers, they slapped it on in order to meet quantity quotas, not quality. So one thick layer of shellac applied over dirt and oil 20-50 yards ago will start to flake when its handled. These rifles were intended to be last ditch ww3 type rifles... they really didn't need a long lasting quality finish.