just one thing, the difference is that Minato doesn't have a Sharingan to help see movements. Itachi had his to see Sasuke's arm moving to bring down Kirin.
The old hand reaction theory huh?
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When the lighting start descending... Itachi only has 1 eye open.
Both are required to be open for Susanno to be used....
His reactions are the best in the manga no contest.