B57 is positionned 1 yard beyond the neutral zone.
The intent of the rule is to prevent B from deliberately causing a false start, while giving B a chance to still get a moving jump on the snap, if they can time it right. The rule uses the phrase "...within a yard..." which means,
very technically, if he is exactly one yard or more, the rule doesn't apply to him. However, philosophically, you'd want to put the burden of compliance on the B player, so I'd probably consider this guy as being restricted by this rule. A solid 1 1/2 yards or more, then put the burden of compliance on Team A.
As TxMike points out, we already have adopted philosophy regarding B players charging toward the neutral zone, but in question as to whether or not the NZ was entered, and causing a reaction by the "adjacent" A linemen as being DOF - even though the rule language requires the B player to actually enter the NZ. So, if the rule doesn't change, you will probably see, at some point, philosophical direction to make the play you describe as a Team B DOF, if he makes an abrupt stop or some sort of abrupt movement ("stunt' as you describe it).
