"...I wonder if Mausers were designed that way for a reason?" Yes, reliability is the reason. Keep in mind these were designed for the Military and function is far more important than looks. That built in tolerance allows that rifle to be operated in unreal conditions. Funny that the next fabulous weapon they designed was the German Luger, something with extremely tight tolerances.
The bolt making contact with the stock varies from one stock to the next. Not a variation from one action to another.