You left out one important detail. The intent to take and retain those documents.
18 U.S. Code § 1924 - Unauthorized removal and retention of classified documents or material
(a)Whoever, being an officer, employee, contractor, or consultant of the United States, and, by virtue of his office, employment, position, or contract, becomes possessed of documents or materials containing classified information of the United States, knowingly removes such documents or materials without authority and with the intent to retain such documents or materials at an unauthorized location shall be fined under this title or imprisoned for not more than five years, or both.
Clearly Biden did not intend to retain the documents, because he gave them up as soon as he knew he had them.