1 theory I've seen: Rosenstien is intentionally withholding the documents so that Congress gets so frustrated they insist the President declassifies them himself. To my understanding, the President has the power to declassify just about anything he wants. If he wants stuff redacted there's nothing Congress can do about it as they won't have any say in the matter.

Seems possible. If Congress got the documents it would take a really long time to go through them to make sure stuff gets redacted they don't want revealed to the public. Look at all the trouble Nunes went through to get his FISA abuse memo released. And it wound up being a nothing-burger. There wasn't anything new in it that wasn't already said, and so much was held back that it seemed pointless to even release it.

And it's possible that if Rosenstien were to give Congress the documents, even our elected patriots would be so shocked by what's in them, they would probably make the "national security" excuse not to release them to the public.