So now that I've had a TON of time to think about this, I get it. If you use the helmet as a weapon, you'll be flagged. If you instinctively tuck your head to brace for contact, no foul.
I OK with it. I hate more rules, but I'm OK with it.
The problem is... Who knows?
It's all a "judgment" call by the refs, and it leaves a ton of "gray area," meaning, room to error by the refs (and also more room to be crooked, fix games, etc... I hate these vague BS rules.