Note how Itachi has exited his Susano, but he is still standing behind the shield. The distance between Itachi and the body of the Susano is about the same as it was in the Naruto, Bee and Itachi vs Nagato fight (At least in the manga anyway).
It was established that he could exit his Susano like 4 years ago. The thing about the Narutobase is that a lot of people will jump right into the "This is a plothole" argument if they don't understand something. Ignorance =/= Plothole.