When you cancel delivery remainder in Call center sales order this does not update retail discounts. It looks like retail pricing considers only ordered quantities and not delivery remainder. Some customers need to track quantity ordered versus quantity delivered. He or she does not delete quantities during the order creation but cancel them to be able to analyze later why the customer has not reached its target (if the customer have not ordered or the company has not delivered).

I hope described scenario is also important to MS Dynamics 365 FO solution. I believe this scenario is common for many companies that try to ensure optimal inventory on-hand to meet customer's needs.