As you were told. you do not call time out. You request it. Only the umpire can call time out. Now what you say is true, that by asking for time you can upset a pitchers timing. But do not assume you will be granted time at every request.
Baseball is a mental game, but it is not in the best interest of the game to allow uncontrolled time outs. Many new HS age players learn this the hard way, the pitcher is in his motion, the batter puts his hand up and steps out of the box only to take a strike when time is not granted..........