When you have a minute, even if you already know your move, you take the rest of the time to read the plays. You don't play your stone until there's only 1 or 2 seconds left, unless the play is so trivial that you need to see your opponent's play in order to continue reading. Every time Sedol played with 1 or 2 seconds left, his rush was only to get the stone on the board, not because he suddenly knew what to play.