If you can "break" the 9 weapons with a sword, technically couldn't you break them using other weapons as well? Like say a spear, whip, chopsticks? The sword is simply a preferred weapon for a user, not a requirement. The philosophy behind the Dugu 9 swords seem to be universal for all weapons.
Isn't the sword the most romanticised weapon in wuxia fiction? All or most of the heroes use it. Such favoritism.