See Vagabond, swords break easily if Musashi swings them. Here swords can withstand blows from Duph's construction beams fired from his mouth lol and withstand rust. More I think about it, its ridiculous lol in a funny way. Swords are treated pretty poorly if you look at Jean's technique being used by Helen when she shows off her Jeanic powers on rocks in the new arc. If you've ever been taught in swordsmanship like I have, you would get savagely beaten by your sensei with words alone for pointing the tip of the blade to the hard surface. Not really meant to do that in swordplay lol