Emergency Purchase Order is showing as mandatory field in FBDI Requisitions template. how to fix it?

Summary:

I am importing requisitions using the FBDI Requisition Import template and would like to clarify whether the Emergency Purchase Order (ePO) field is mandatory.
I have tried multiple combinations during the import. However, whenever the requisition Status is set to Approved, the Emergency Purchase Order (ePO) becomes mandatory. If I leave the Emergency Purchase Order (ePO) field blank, the import fails with the following error:
"A unique purchase order number must be provided for the specified sold-to legal entity."
Could you please confirm whether this is standard Oracle behavior or if it is due to a configuration or customization in our environment?