I don't know if it is really relevant but in Book 1 of the Bane-Triology there is a part where
the sword master explains to Bane one of the bigger advantages of dual bladed
weapons.
I don't know the exact wording but he said that dual bladed weapons are kind of exotic
and most people don't have the necessary experience to defend against it.
Against a single opponent the second blade is useless but it confuses unexperienced opponents
because they are sometimes distracted by the second blade because it looks like there was more than one
blade the can harm someone even if it can't.
Like I said I don't have the exact wording in my head but there were a couple of pages for that kind of weapon
and its combat application.