Got a “Test dev” notification from Airbnb:D
twitter.com
twitter.com
Making it a permission just makes it default -off rather than default -on
In general, I found vibration-only to be pretty much the default for a lot of people I know (though I am sharply aware that this is just anecdata and doesn't say much about the real state of things). I tried googling whether there was some breakdown of notification vibration vs sound smartphone users, but, sadly, couldn't find much.
People make mistakes, it's ok.