I have had nothing to do with creating this package, so can only share in my ignorance of the details.
Partial shipments, or perhaps shipments from multiple points may be a reason for this behavior. On some orders, one may have to ship from point A to point C, and other similar items from point B to point C. This happens, for example, when stock is distributed to multiple points for inventory, and then a single order requires fulfillment from multiple points.
In any case, I hope the behavior doesn't change, because it seems to be setup for anticipating many possibilities which might otherwise be more complicated to adapt to within the system.
