Scrollview does not automatically re-center itself with any setting. This is something you have to do yourself. You can use SpringPanel to make it do this, but you have to do it manually.
The None, Momentum, MomentumAndSpring only covers how the behavior is when you drag the scrollview, so momentum adds "weight" to the panel, so it doesn't stop instantly when you release your touch, momentumAndSpring makes it possible to drag the panel contents within the scrollview like in iOS, but makes it bounce back to fit the edges.