I don't think it's as bad as that statement implies. It's not all smartphones or laptops or TVs or cars. A large number of those devices would be things like smartcards, LED light bulbs, USB cables, ID tags for shipping containers: tiny, low-to-no-power devices, if what you are concerned about is large amounts of electronic waste.
True if you look at processors in general. I'm not sure it's true of Arm-9 processors, though. I think they're a bit overpowered for a LED light bulb, a USB cable, or an ID tag.
Not necessarily. A new car can have 100+ processors in it (though I don't know how many of them would be Arm-9). One CPU != one device.