Price List Validation Org - Not working with REST service /fscmRestApi/../priceLists

Summary:
In the UI, we can add items to a price list where the item validation org has not been setup at for a specific BU.

If we try the same using the webservice for pricelists it errors on the item validation organization.

If we setup a BU specific validation org, then the REST service works as expected.

Has anyone else come across this? We'd rather not setup each BU to have it's own validation org.

Code Snippet (add any code snippets that support your topic, if applicable):
Calling: /fscmRestApi/resources/11.13.18.05/priceLists

API error message - 

"o:errorDetails": [

        {

            "detail": "The value of the attribute ItemId isn't valid.",