Using shipping method that charges per item on handling cost, why is there a Handling Cost calculated on an item with null handling cost on the item record?

Symptoms:
1) Item Record > Basic Tab > Handling cost is null.
2) Shipping item used is set to charge handling cost per item.

 

If the item record does not have a specific handling cost value or null value, then the shipping item used on the sales order will trigger the handling cost calculation.

If you do not want the item to calculate handling cost, enter zero as handling cost in the item record