Especially, why would he say that when he also said he had mentally declassified all the records anyway?Hmm, it appears the Presidential Records Act states that all official records are owned by the National Achives.
First sentence is "Presidential Records Act - States that the United States shall reserve and retain complete ownership, possession, and control of all Presidential records".
Second paragraph:
Requires the Archivist to assume custody, control, and preservation of and access to the records of a President upon the conclusion of the President's term of office; making such records available to the public as rapidly and completely as possible. Requires the Archivist to place such records in a Presidential archival depository or another facility operated by the United States. Authorizes the Archivist to designate, after consultation with the President, a director for each depository or facility.
If your take is true, why did he say he shouldn't have the one document (assuming the transcript is accurate)?
Nonetheless, whether classified or declassified, the documents are still property of the U.S. government and he still shouldn't have them.