I can't tell you for sure if this story is misinformation or not. That's part of the problem with misinformation. Well constructed misinformation is not easily proven false.

What I can tell you is that it is absurd to believe it is true given what we know about the details surrounding the "discovery" of the information.

I'd be with you if the Biden campaign denied the material's legitimacy. So far, at least as far as I'm aware, they haven't.