I think there should be a third option, which is to treat them like normal notifications. This is so obvious to me that I'm utterly baffled that it isn't an option. We probably wouldn't even be having this discussion if the option existed. But it doesn't, so here we are.

I would even OK with deafening noise being the default. I would argue that it shouldn't be the default, as I think the false-alarm problem is a serious one that will cause people to just turn it off. But I understand the other side of the argument.

My opinion is anything that causes a bunch of deafening noise from every phone in the vicinity should be treated with the same level of gravity as turning on the tornado siren. We don't turn on the tornado siren for every kid who gets lost or every flooded road. We shouldn't be blowing up every phone for those events, either. Tornado coming to town? Ok, blow up the phones. Missile coming down from the sky? Ok, blow up the phones. City-destroying wildfire coming in? Ok, blow up the phones. Kid got in the wrong car? Berry St is flooded? Sorry, those doesn't qualify for the tornado alarm, so they don't qualify for blowing up phones either.