They may give reasons for denial (in writing) that differ entirely from the reasons for denial in your file.   It is my a posteriori understanding you are only entitled to the real reasons for denial if you request the file under FOIA. 

Thus it is in your best interests to request the file asap.  In this way, you will be informed enough to contest and adequately address any incorrect reasons for denial in the course of your appeal, should your agency's process grant that opportunity.