The wording of the rule is along the lines of the pitcher having both feet on the pitching plate and taking the sign or 'simulate taking the sign'. This is to prevent girls from using a 'walk-up' to initiate the pitch. I don't think there is any mention about length of pause...
As for 'presenting the ball' - common misconception and no such thing required. The ball can be in either hand when the hands come together to start the pitch. Some pitchers purposely never take the ball out of their gloves upon receipt so the batter will only see it at delivery.
Any blues out there that can quote chapter and verse?