Infield Fly is the correct call, but what they are saying is, if the ball is fair. If the ball goes foul without being touched, it is a foul ball. Just like a ball being close to the line and they still need to call Infield Fly, if fair.
The batter must be in the running lane after they reach haflway to firstbase. Interference is called and the batter is out and all runners return to the base they were on when the ball was put into play.
Ball is dead in either case and if the batter's foot is entirely out of the box, the batter is out. I'm not sure the homeplate umpire saw how it occured.