fair/foul - then catch/no-catch

[EsqUmp]

It is important to signal fair/foul because of the potential for the defender to bobble the ball and drop it. It is possible that the defender initially touched the ball fair and then dropped it over foul territory. By sticking your arm out and pointing, the umpire will know whether the ball is fair or foul in case it falls. That is much better than a defender diving for the ball, bobbling it and dropping it only for the umpire to stand there wondering, "Hmm, was that fair or foul?" Your brain may not remember, but if your arm is sticking out, you'll have your answer.

In MLB, if the catch becomes obvious, they do not signal "catch" after the point.

A good case in point is when the Yankees were playing the Red Sox and Jeter initially touched a ball in fair territory, then ran into the stands. Fielden Colbreth pointed fair, then ran over toward the stands. If the ball had fallen, it would have been fair.