changed to automatically ZERO any items that were not available for delivery

I also see that "Action for balance" has two options "Automatically Backorder" and "Cancel items not delivered"

I think we need a third option "Ship Complete" or some other better description that would allow the previous
behavior such that I would have to Manually change the quantities as needed.

Why?

I often have missing items that were delivered but not yet manufactured in FA, so I pop open another tab, make it and then click UPDATE on the delivery page, commit and I am done

Does this sound useful?

If not I am sure I can change my behavior, but a Ship Complete option may have uses

Tom