He probably gets confused because impeachment is considered a "judicial proceeding", derived from the senate trial. It's the reason why, as in the case of the Clinton impeachment and as is happening now with getting access to the Muelar report etc, the exclusions of some ruling 6e applies to being able to get unredacted documents and grand jury testimony when doing an impeachment inquiry etc. You know. I know far too much about all this crap now.