After reading this, I'm wondering how a phone could differentiate an Airtag following me from for example a guy with an Airtag sitting somewhere near me while inside a train for two hours.
I believe the tracker doesn't emit the same signal when the phone the AirTag is paired with are communicating directly. So as long as the owner of the airtag is in the vicinity it will not be considered as following/stalking you.
> For now, if an AirTag you don't own "is separated from its owner and determined to be traveling with you," a notification will tell you this and that "the owner of the tracker can see its location."
It only notifies you if the air tag is without ite owner. If this wasn't the case I'd be getting notifications left and right for my wife's airtag. Instead I only get notifications when her phone is left behind but her tag is with me.
It warns you but it doesn't contact the police for you. It's still up to you to assess the situation and your next steps. If you're on a sleeper train or have any reason to believe it's not a threat, just ignore it.