Aww that would be tight to see Itachi freak out to find out that there is another way to Magnekyou Sharingan(WITH NO KILLING!!!).
Well, like I said, maybe he tricked the system in a way. It's possible that since it was his fault that Obito died, since he pushed Kakashi out of the way, that maybe that counted as him killing his best friend. And, he didn't know about that ability until he fought Itachi.