It's easy to find out if someone is driving as though they are impaired, less easy to find out if they actually are. Medical emergencies spring to mind as something that will be hard to distinguish.
How many people rushing to the hospital with a pregnant wife in the back will no longer make it before giving birth?
My reading of this article is that “kill switch” here seems to be “car determines that you are driving like a drunk person, so shuts down” rather than “some service remotely sends a kill command for reason X to your car”.
In the hypothesis that it’s actually kind of easy to figure out if somebody is impaired, I’m pretty conflicted because the upside of not having an impaired person driving is really high. Just I don’t know how possible it is, nor how reliably that would work. On top of that it seems like one step between that and “and the car reports you”.