When Antrel Rolle was with the Giants, he often spoke about the mental toll of having to prepare to play two positions. He was asked not only to cover his safety responsibilities but at times come down to the line of scrimmage and play nickel cornerback. It was difficult for him to carve out time to work on the disparate skills for both positions and study the playbook for them.
Rolle was a Pro Bowl player and an established veteran when he was asked to do those things.
Bennett Jackson is not. He hasn't even played in an NFL game.