First things first, Focus Points do not control or set the aperture, so have no control over DOF.
All they do is set the focus.
The DOF is controlled exclusively by the aperture, which is set either manually or automatically depending on what mode you have set.
The benefit of multi focus points is that you can move/select where you want the main point of focus to be. This does away with prefocussing and then re-composing.