Grand jury testimony is supposed to be secret.
Therefore, any revealation of what is going on in the grand jury has to be from an anonymous source or else they're going to jail.
However, you cannot tell a real anonymous source with actual information from a bogus anonymous source that the reporter made up. So you have no idea if the latest article based on an anonymous source is factual or pure BS.
So we're all just speculating.
Why hasn't Novak been summoned to testify?
The general rule is that a witness is free to publicly recount what he told the grand jury. THe secrecy obligation attaches to the jurors, DA, and others who hear the testimony in the jury room.