Does OM:Enforce Check For Duplicate Purchase Order work during copy orders

We have the profile OM:Enforce Check For Duplicate Purchase Order set to YES at the Site level When we create a Sales order with an existing Customer PO number for the same customer, we could see the message popup for duplicate PO However, when we copy the order we are not getting the same message, I couldn't find any note that it will work for copy order Can any one clarify on this Thanks