100% WRONG!
Itachi would have killed Sasuke, when you look at their fight, you can't say he was holding back, espically since after he died he litterally showed nothing but a new genjutsu.
Did you see the way they were throwing those shuriken?
Tsuyomi got broken, Sasuke pupil is bigger than Itachi's and in CM its twice the size. Curse mark is like sasuke's tailed beast. So I agree to that but he lost curse mark and he has susanoo which is also likea tailed beast.
Sauske also has another type of sage mode or curse mark or something:
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Itachi was indeed said to be holding back, but at what link? I believe only with genjutsu. If he was serious he would have did that genjutsu.