I think terms like these get a little too generalized when really shutting down half the field might be more applicable to some one like Richard Sherman than Darrelle Revis.
Sherman tends to stay on his side of the field, while Revis (or Talib) might more often find themselves following a single receiver wherever he lines up. So Sherman might “shut down half the field” while Revis might “shut down the opposition’s top target”.
Both are somewhat hyperbolic, but the general idea is the same, that a cornerback is so good passes can’t be thrown at them.
