Board Thread:Theories and Speculation/@comment-36512555-20200328202326/@comment-1207741-20200329205732

Where does he say he's going to use Tsukuyomi? And not all genjutsu used with the Mangekyo active are Tsukuyomi, as shown by Sasuke's feather genjutsu in 413.

Even if he does say it, I see no reason it isn't still a mistake; the same mistake can be made twice. Given the option between doubting the text and doubting the art, the art tends to have a greater chance of error.