I have a use case where I need to extract document properties and owner information based on various filter criteria. This requires the following process:
1) Query the API for the document IDs that meet my criteria
2) Loop through the result set and call the document API for each document
3) Locate the ID of the owner of each document
4) Call the users API for the user details
If owner__v were queryable, I could potentially limit all of this to a single API query call that joins the document and user objects.