because someone has to go through those records and manually redact things they cannot legally disclose. Figure out what is responsive. What should be removed because it's not actually related to the request. ETc.

Also they didn't get access to part 1/n. They got access to part 1/?. And then 2/?. And then 3/?.

> what about spoonfeeding the records?

Just a guess. If the facts explained in those records prescribe after four years, agents must be tempted to release the part N/N in four years and a day. Without knowing the full history any demand could be dismissed.

Not different than nuclear companies adamantly repeating for the first years that no one was killed by a nuclear accident.