As far as I remember the ruling was a bit more nuanced than most reporting on it. It was that the car is not a container that removes a person from a public space when the car is in a public space. If you are in a public space then your gun needs to be cased or you need a permit.
It’s easier (maybe?) to think of it reversed like trespassing. If a person is not allowed on your property they can’t walk onto it, that’s obvious right? What if they drive on, are they no longer on your property because technically they’re in a car and only the car is on your private property but the person inside isn’t?