I was reading through the Dungeon Master's Guide and I came across a magic item, the vorpal sword. The description states that it is a magic weapon. If I am not wrong, magic weapons bypass resistances and immunities against damage types, but in the description it also states it ignores resistance to slashing damage. Am I missing some point?
Why would the Dungeon Master's Guide specifically state that the vorpal sword ignores resistance to slashing damage?