Agreement creation API Response "Invalid attribute \"EnableAutomaticSourcingFlag\" in the payload."

Summary:

Unable to Set Enable Automatic Sourcing & Punchout Requests Only Flags using the Agreement creation API

Content (please ensure you mask any confidential information):

Using an API to create Contract Purchase Agreements does not seem to be able to change the following fields from system defaults:
1. EnableAutomaticSourcingFlag
2. PunchoutRequestsOnlyFlag

When non-default values are passed against either of these fields, we get a error response of
"Invalid attribute "EnableAutomaticSourcingFlag" in the payload."
"Invalid attribute "PunchoutRequestsOnlyFlag" in the payload."

It is essential to be able to change these to checked & unchecked based on business requirements and we must be able to be able to do CPA creation through APIs.