Rosenstein is sticking his thumb in the eye of Congress. He is saying that if they want to play hardball over documents, he will show them who really has the power. As in threatening to subpoena congressional aides, or gum up the works with an avalanche of documents. He gets to tweak the president’s nose, show up Sessions, and in general thumb his nose at Congress. And all with no fear of contradiction — just helping them do their oversight, dontcha know?
IOW, Rosenstein is a vandal.