There are various throwing angles. Which one they use for a given scenario depends on how they catch the ball—high, medium, low—and where they intend to throw it.
If a player catches a ball above her head, for example, it doesn’t make sense for her to throw from a low arm slot. In this case, a mid-body position is more effective because she can get the ball off to her target quicker.
To ensure your players can react quickly no matter how they catch the ball, it’s wise to train them to throw from a variety of angles.