Board Thread:Naruto Discussions/@comment-25645405-20141128183407/@comment-3279282-20141201211702

Seelentau wrote: Amaterasu is Blaze Release for a really simple reason: When Sasuke was trapped in Kaguya's ice, he used Amaterasu with his left eye and Kagutsuchi with his right eye. He didn't call it Blaze Release: Kagutsuchi. This was the first time he did that and it was also the first time he used Amaterasu before using Kagutsuchi. So why didn't he call it Blaze Release: Kagutsuchi this time? Because he had already released the black flames by using Amaterasu. Blaze Release - as the name suggests - is what releases the black flames and Kagutsuchi is what controls them. There was no need for a second release of the black flames in this case, since he already had them before his very eyes. Do you see where I'm coming from?

The difference is that in this case, we're using what the manga gave us and not real life logic.