The reason I recommend extending the primer de-caper pin is to avoid the pressure that the primer can produce and direct the gasses downward in a safe direction. I have been loading over 50 years and have never had a primer go off during de-capping and don't want the first time. they are strong enough to jam a bullet in the rifling and I have removed these from barrels that were lacking a powder charge so I know how hard they can jam the bullet when everything is sealed by the case.
I don't know if it could damage the press or injure the re-loader but again I don't want to find out. I have seen and heard about it happening and the results were not good, so better safe than sorry. I personally don't like spraying anything in the case that might contaminate powder later even if it is solvent cleaned, so I take special care when de-capping primers.
Just Me
J E CUSTOM