From the report page 65 Biden says:
"They didn't even know I have this" In reference to notes he knows he shouldn't have still
Then on page 77 biden says: "I didn't want to turn them in" again reference to notes he should not have retained.
These are both from audio recordings, so there is actually plenty of evidence to suggest he willfully retained classified docs he knew he shouldn't have.
I'm assuming you didn't read the report before making this comment.