Unable to suppress agreement email notifications

We would like to suppress the notifications generated for agreements when created through our integration with the Adobe Sign API. Per the documentation, we are setting the fields that should do this in POST /agreements:

"emailOption": {
  "sendOptions": {
    "completionEmails": "NONE",
    "inFlightEmails": "NONE",
    "initEmails": "NONE"
  }
}

However, signees still receive email notifications from Adobe, and the API response to GET /agreements/{agreementId} does not include an emailOption field. Is there anything that could cause the emailOption field to be reset or ignored?