Strictly as described, FST --- the defender has to have something in the NZ, now that could be the tip of his finger and don't split hairs on "if he was in" but the rule is fairly clear on that. For the defender to "move forward" and not get in the NZ at all he would have had to been aligned a good distance away from the ball. Not common but definitely happens, if he was aligned tight and moved forward he would definitely be in and it would be DOF. Leave the protractors at home, aligned tight, any movement forward and A reacts stick it on B.
2. No player may enter the neutral zone causing an offensive lineman to react immediately or commit any other dead-ball offside foul