None of it has to do with whether or not she was outed, which was the original reason for the investigation. Fitz is either obsessive/compulsive or he is looking for fame, glory, and an extended contract.
What's so freakin' difficult about going into the grand jury and either telling the truth or saying you don't recall? That seems pretty simple to me. I'm amazed at the number of FReepers who are willing to give Libby a pass even if he lied to a grand jury. A lie is a lie. It's a crime. It's the law. If you don't like it, go do something to change the law (although I will oppose you). Don't blame Fitzgerald for trying to enforce the law.