I've just read Yuan Yang Blade about this pair of prized blades and how a few jianghu people try to steal the sword.

One of the martial arts mentioned, the most powerful in that book, was husband wife blade skill. It was very similar to LCY's jade arts she developed that was later used by YG and XLN.

Is this a case of Jin Yong running out of ideas, or purposeful, but some how down the YG line, it changed from sword arts to sabre arts.