In the whats new the following is shown for local relationships

I note that

Set pbUseDDRelates to True
is used in Vendor and Customer

Is it necessary to set these in the top level DDs also for this to work correctly?
There seems no need to set thse for those DDs as the do not have any parent records

Code:
Usage
This shows how you could create all local relationships in the order entry view. As mentioned, you normally would not want or need to do this and this is shown as a sample only. You do not need to set all of the DDOs as done in this sample; you could actually set any single DDO in this example to use local relates.

Object Vendor_DD is a Vendor_DataDictionary
    Set pbUseDDRelates to True
End_Object    // Vendor_DD


Object Invt_DD is a Invt_DataDictionary
    Set DDO_Server to Vendor_DD
    // define local relationship
    Set pbUseDDRelates to True
    Set Field_Related_FileField Field Invt.Vendor_ID to File_Field Vendor.ID
End_Object    // Invt_DD

Object Customer_DD is a Customer_DataDictionary
    Set pbUseDDRelates to True
End_Object    // Customer_DD

Object SalesP_DD is a Salesp_DataDictionary
    Set pbUseDDRelates to True
End_Object    // SalesP_DD

Object OrderHea_DD is a OrderHea_DataDictionary
    Set DDO_Server to Customer_DD
    Set DDO_Server to SalesP_DD
    // define local relationship

    Set pbUseDDRelates to True
    Set Field_Related_FileField Field OrderHea.SalesPerson_ID to File_Field SalesP.ID
    Set Field_Related_FileField Field OrderHea.Customer_Number to File_Field Customer.Customer_Number
End_Object    // OrderHea_DD
   

Object OrderDtl_DD is a OrderDtl_DataDictionary
    Set DDO_Server to OrderHea_DD
    Set DDO_Server to Invt_DD
    Set Constrain_File to OrderHea.File_Number
     
    // define local relationship

    Set pbUseDDRelates to True
    Set Field_Related_FileField Field OrderDtl.Item_ID to File_Field Invt.Item_ID
    Set Field_Related_FileField Field OrderDtl.Order_Number to File_Field OrderHea.Order_Number
End_Object    // OrderDtl_DD