I know everything there is to know about the swords, thank you, I was asking why he needs to keep switching between during his singular assault on Sephiroth during the V5. The whole idea just strikes me as lame and unnecessary.

Maybe if he had separated his sword to startle Sephiroth (which he did and I suspect it was the original purpose) and started recompiling his sword, that I could understand. But switching between every last sword in his arsenal for no reason just confounds me.
Like I said before, some swords are just better suited for certain things. The switchblades are easy to get swords that provide the wielder with another weapon quickly. However, it is small, where the impact blade would be more useful as it is longer. The two serrated blades are used if damage is what you really want, or if you need to disarm your enemy. Every piece of the whole assembled sword is made to be better in certain situations. With each piece that is connected, the sword becomes better. When the sword is complete, the weapon is at it's maximum best, if you will, and is more powerful than any minisword individually. And like you said, this entire aspect of the sword itself gives the wielder the advantadge of surprise, as no one would expect such a thing, and it provides many sword to be used when needed.