My gut (as well as some members of Congress  ) tells me this is all related to the Hunter/Joe corruption investigation that's expected from the House now.

Once subpoenas and warrants start hitting the DOJ, these documents would have been found anyway.  This is a house-cleaning operation, and the cleaners were not legally able to destroy the classified -- so they had to report the documents.

Trying to keep the scope of this focused on handling of classified docs gives the Biden's time to scrub all the incriminating evidence of corruption, influence peddling to foreign actors, and money laundering.