The point of all this is narrative. They are always doing things to put the anti-Trump public's complete trust in Mueller and Rosenstein. It's at the point where the left is 100% convinced that Rosenstein is /theirguy/. ANYTHING that comes out in favor of Trump and against the cabal will have more validity and the public and media will have zero grounds to argue against it.
This is the point of Trey Gowdy playing devil's advocate.
This is the point of the 'bad' relationship between Trump and Sessions.
They are making it where it's Trump vs the good guys and at some point the 'good guys' are going to reveal the truth to the public.