Hi Jason,
When you try to Bind your context node with interface, you get the related data in collection because that interface belong to the same component , as your context node.
But when you bind it with the component usage (here component usage is mainly used to call an external component in your component) , component usage will access the data of the component that you called in your component so , it is obvious that it will have that component data.
Hope i'm right with this, because its just a common sense .
Regards