I think the doubledown has the two halves of the handles tied together with interlocking gears, so you cant do any fun balisong (poop) with it. Plus the handles lock, so definitely more of a tool than a balisong. Marketed as a folding machete.
Why would the samurais or ninjas or shaolin carry long knives also. Why couldnt they carrys pocket knife.
Cant a person want something and not know why he needs one. Lol