It's not about having the documents, it's about obstructing the government's effort to retrieve the documents.
Biden and Pence are cooperating, and Trump declared on TV he not only had the right to take them, that he deliberately took them, there is a telephone call on this, maybe a tape or two ,and his staff helped him, before and AFTER the subpoena. The DOJ will not prosecute for the inadvertent owning of national defense information documents by members of the exec branch, but they might if a former exec branch member doesn't cooperate, and goes around lying about the PRA that he, as president, has the right to take them (no, he doesn't).