Does it matter that former President Trump states that he de-classified the materials found at Mar-A-Lago?

No.

Section 793(d) is not restricted to classified materials. Rather, it covers any document “relating to the national defense” that contains information that the possessor has reason to believe would be detrimental to the United States if made public. Here, the search warrant return states that documents seized from Mar-A-Lago include “classified/TS/SCI documents” (meaning Top Secret or Secure Compartmentalized Information), “Top Secret Documents,” “Secret Documents,” and “Confidential Documents.”

Even if former President Trump de-classified these documents before his term ended, the information contained in those documents would still fall squarely within Section 793(d).