Hi,
If you have 4013 and 4014 as "YES", your Owner and Controller can submit request for their own FF IDs.
Like in access request, it is not possible to restrict the Controller from approving his own FF logs.
We also have same scenario, where 2 controllers are assigned to same FF ID and when one use that ID. logs are reviewed by another controller, but both will have access to approve the log reviews.
We have raised this to SAP and they asked us to request for customer enhancement 
Regards,
Madhu.