Steel is harder than lead so it shouldn't be a surprise when lead breaks apart when it hits a piece of steel at high velocities. I bet you could do the same thing with a factory produced Combat Knife.
Katanas are just like any other sword, they just have better PR than other swords for some reason. It's insane how people really believe that a katana can cut through anything harder than bone/leather/wood in human hands. Find me one video of someone cutting through (by this I mean swinging it themselves, not propping it up and ramming things into it with machines) a reasonably thick (1 inch) piece of iron/lead/brass/bronze with a katana without the blade being horribly damaged/broken, and I'll get off my soap box.
Regardless, I suppose it will be fun to be swinging a sword around in this game. Although, I'm not sure how much more(less?) effective it's going to be than the Fire Axe/Chainsaw.