Once you have "swung" a bit.., I don't really think sharpening the swedge is much of a factor at all..., but it is good to practice a little with a double-edged model when you start getting proficient.
It gives you more feel and facilitates less reliance on ricocheting the unsharpened spine in performing manipulations.
It is simply a different feel for the inertia of the piece you choose to practice this with, and IMO..., will smoothen your actions with all Balisongs over a period of time.
"Hunters seek what they [WANT].., Seekers hunt what they [NEED]"