New document using AutoCreate - Blanket Release - Automatic. Operating Unit

Hi, I have a question regarding the creation of new documents and the behavior of the Purchasing Org field.

We use the Global Procurement responsibility and we use "Auto Create" function. After using this function we can see a form "Find Requisition Lines" (POXBWVRP). The responsibility can use many operating so we choose the value from the LOV in the "Operating Unit Field". Then we use "Find".

Next on the "AutoCreate Documents" form we choose a requisition and we choose the parameters like "Action=Create" and "Document Type=Blanket Release". Next we choose the function (button) "Automatic". Once it is clicked we can see "New Document" form and in this case the "Purchasing Org" have the value defaulted from value selected earlier in the "Find Requisition Lines" form. The "Purchasing Org" in this case is greyed out and is not editable.