Fair does, but the ball just tends to come straight back in causing the defence to work harder whereas if we leave someone up to hassle the opposition players, especially someone fast like O'Brien or Clarkson who can close down the defenders quickly, it slows down the return ball and lets us reorganise. It also forces them to leave more defenders back reducing the number of targets that the dead ball taker has.
It isn't just McGee who has used this tactic, Malpas and Butcher regularly did this as well.