Document Of Record missing in form submission payload

We are using a form data model to bind fields to both the submission and the automatically generated document of record. However when it comes to submitting the forms to an endpoint the resulting payload does not include the generated DoR file alongside the JSON form data.

When configuring the guide container for a form you can specify what you would like to submit alongside the form fields which have been bound to a form data model. In this example we are trying to submit the Document of Record alongside our form. This requires a DoR bind Reference to be configured, however, this is unclear as to what should be selected here. Binding to our top level model object causes an error which says 'Selected ref must of simple type'. Binding it to a string property does not produce a DoR within the form submission payload. 

Does anyone have any thoughts/suggestions for solving this issue?

Context: AEMaaCS