Unauthorized accounts must not have the Restore files and directories user right.
Inappropriate granting of user rights can provide system, administrative, and other high-level capabilities.
Accounts with the "Restore files and directories" user right can circumvent file and directory permissions and could allow access to sensitive data. It could also be used to over-write more current data.
How this relates to the STIG checklist: STIG vs SCAP benchmark.