Therein lays the problem with hypothetical questions. As FLAHL suggests above, "Here's my rationale - B3 "backed across the sideline" so he wasn't going to tackle A1, who was 3 yards away. A1 went OOB anyway, so there was no advantage gained. To me, this is nothing. It's like holding away from the point of attack. May be worth talking to A2, but that's it."
Everyone is required to ALWAYS know EXACTLY where ALL the lines are (which are ALWAYS presumed to be EXACTLY straight), but in the absence of any advantage being gained, or any inappropriate intent to harm, do we advance the game more by a well placed "word to the wise" or a conspicuous penalty?
If you CHOOSE to adopt a "One size fits all" policy, you can, but it will likely hamper your judgment a lot more than it will clarify it.