User blog comment:B214/Question and Answers 3/@comment-106.79.73.110-20140714034941/@comment-16281343-20140714042440

^ Nope. That theory doesn't work.

Issei being able to use Gasper's SG was already explained in Volume 16.

And also Issei isn't particulary good with dragon abilities. As of now, he only has one technique that can be counted as a dragon ability and that's Flame Blaze taught to him by Tannin.