OData connection to list not returning user data

Our reporting team is trying to use the ListData.svc (https://MySharePoint.domain.com/tools/ProductivityTracking/_vti_bin/ListData.svc/TimeTracking) to access list data for a report. They have no issues accessing the data. Their problem is no user data other than the ID is returned for columns like Created by and Modified by. 

If someone could show me the ways of the force, it would be much appreciated.