Filtering by email in User Directory does not work for administrators when emails are being obfuscated

Steps to reproduce :
1. Go to Global Administration -> Mail -> Advanced
2. Choose to obfuscate email addresses
3. Save the changes
4. Go to Global Administration -> User Directory
5. Notice that Email is one of the fields listed to be displayed in the User Directory table
6. Filter in the User Directory table by email

Expected result : only the users matching the given email would be displayed.
Actual result : the results are not filtered by the given email.