A great point, and perfect proof what a sham this announcement is.
The IG can’t investigate the CIA, which (under Brennan) sentin Halper to try to sabotage Trump. The IG can’t investigate the State Department, which is complicit in the 2nd dossier and Downer’s bs trap. It can’t investigate anyone outside the doj or compel testimoney from anyone not currently employed.
In short, Rosensessions just screwed Trump again.