I'll reveal everything behind the development of that.
Back then when that content was developed FS3's story was just barebones. I only had the main core concept of the story. All the characters had no personality yet. (Note how Silvie actually talks, in which I was forced to add the telepathy ability in FS3 since I decided to make her mute wayyy later on). This also applies to Zephy and Capelle, I had no idea where I want to put them in the story and wanted them to have the star power of Day and Night back then (Note that Capelle doesn't even use dual guns in that battle). As for Hope arc characters like Luze and Hexia they didn't even existed in my mind back then. Those characters were born specifically for Hope Arc in FS3. The same thing is applied to Zeto's light transformation. Originally I had planned him to have that ability but it was scrapped. This is due to Zeto's personality and also I didn't really like the design of the transformation that much. >_>
My original plan was that FS3 would also have this exact same battle with a story in FS3 team's point of view, but I guess it didn't happen D:
In the end I closed FS3 like that and decided to move on to Fragmented Dreams.