Titanic was a “triple screw steamer,” meaning it had three propellers - port, center and starboard. The port and starboard propellers were capable of being reversed, while the center propeller could only propel forward. You can see this in the 1997 movie as they show the props when they throw the ship into reverse.

The center prop (that only goes forward) is the one directly behind the rudder, so the theory is partly that they lost some steering advantage when they lost the center prop.