Have they said if they're sending the missing bits directly or using the distribution/fulfilment centre? The latter would probably make more sense but I imagine could end up taking longer (than your Aug 1 purchases).
Looks like you were probably right about them sending the missing pieces to fulfillment centers. That or I'm completely wrong about what they called a "complemental package". One can only hope that they're a little more forthcoming about when the order corrections will actually hit a mailbox.