So what? There is no rule that a private citizen even a CEO, must not use an alias screen ID. Now the Secretary of State (Hillary)?, that is different.
They may not want to poke the email beehive too hard, now that Preet is out in the Southern District of NY and whoever Sessions puts in there will no longer slow-walk the Clinton investigations. Maybe in a few months we’ll start to see justice done in Hillary’s case.
Of course this is why Preet is putting up such a fuss.