Ok, people do indeed assume that it is a requirement because of a misconception from Itachi. But people like me, get this idea because the Databook says so. (Page 274, in case you are curious) Also, when Madara says, "You need both MS sharingan to unlock the Susano'o" that is because you do need both eyes. But you are failing to see that having both eyes satisfies the Amaterasu + Tsukuyomi req. 1 eye has Tsukuyomi, the other, Amaterasu. Furthermore, just because he doesn't explicitly say "Tsukuyomi" doesn't mean that isn't the tech. When Sasuke was using his techs in the Bee fight, they were the first time he used them. So Kishi was just showing us that Sasuke can use the techs. Also, to counter your "Sasuke didn't say Tsukuyomi, so that means it wasn't" Here is Itachi just talking about what the genjutsu is, but he doesn't actually say "Tsukuyomi!" when casting is. He just does:
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And as you can see, Sasuke was hit with Tsukuyomi and during that entire encounter, Itachi NEVER said "Tsukuyomi!" So your DBZ logic fails.
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