Agreed, but if there are 1 of 10 boxes and only 1 box has a full C.O.D amount for the entire shipment, what is the shipping cost difference versus putting a 1/10th C.O.D. amount on each box? I don't know the answer to this.
If there is a huge difference in price but only one check collected is needed, UPS should make this easier to do in the shipping software at a minimal cost, to show a C.O.D. on each package of a group shipment. That's just good proactive customer service.
May be they already have.