No email addresses in results from /restapi/vc/users/visited endpoint

When I get the results from this endpoint, there are sometimes no email addresses for the returned users.  On certain communities it does come back, but for others it does not.

Are there permission controls on the results?  To clarify, if the user credentials being used for the API call don't have permission to see this data, could this be causing the results to come back without email address?