It's got literally nothing to do with the opposition at all, it's not to try and be unpredictable or otherwise. It changes the angle you're able to deliver the ball into the box at, and as GazzyB said above it forces them to pull 2 defenders out of the area that we're trying to find space in.
If we handed a note into the away dressing room before the game and told them we were going to do that with every corner, it would still change the angle, and they would still have to pull defenders out the box. It's got nothing to with anyone knowing.