Another provision of the 1996 amendments calls for improved annual reports. The old reports did not contain enough useful information, and Congress finally got around to asking for better data. Some of the new data elements are specified in the statute, and Congress told the Justice Department to establish additional requirements. Unfortunately, the responsibility fell to the Office of Information and Privacy at Justice. OIP told agencies to report the costs of FOIA processing but only the estimated costs of FOIA litigation.
Justice incurs most litigation costs.
My guess is that it doesn't want to be held to the same standard it sets for everyone else. The second example is a little more political. OIP told agencies to calculate the percentage of total costs recovered by FOIA fees. FOIA is not a fee recovery statute. Many requesters are charged zero or nominal fees.