I don't know why GS worked in my test without error message but I know why HR works without error in your system while GS has an error message.
SAP checks in general for all partner roles with the partner type LI if this partner has purchasing views for the same purchasing organization as used in the PO.
This check is technically done in LWY09F01
And exact here has SAP defined some exceptions for certain partner roles.
The exception for HR came with OSS note 2029827 - Allow partner function HR (manufacturing organisation) to be assigned without purchasing organisation data in the vendor master data