User blog comment:B214/Question and Answers 2/@comment-86.81.216.93-20140529174533/@comment-24098614-20140530014928

It is thankful for both Vali and Issei to achieve both of these attacks because the original attacks that the Sacred Gears came with was fatal to both Vali and Issei so they had no choice but try to evolve them because of how deadly it was to both of them.

The case of Issei evolving this original attack it was due to his incredible imagination because his hentai nature might have saved him a small way and it contributed to this evolution because he did the unexpected. I knew that Vali would eventually evolve his attack because Vali might be a battle maniac but he has brains to go along with those skills.