"I don't know exactly how things ended originally in the world the other you was from, even if we hadn't been interfering in the singularity, it probably would have been different, anyway. I just know that some of the Masters died, and the Holy Grail had been corrupted and caused some kind of disaster at the end."

After all, for there to be an El-Melloi II, then that would mean that the original El-Melloi was no longer around, so that much was a given. Ritsuka just isn't privy to how the mage was killed.