Hmm. That's interesting or "stupid" as you put it. I mean, you are helping the environment regardless of where you buy the car as long as you like in Cali or Wash, why would they care? Probably other motives. Okay. At least for me in Colorado, no matter where I've actually purchased a car, I've paid the taxes based on my location of my current residence.
Ahh ... I see what you are talking about with Oregon. But still, I would think you'd have to register it where you live, and pay taxes based on that. Sales tax based on where you live for cars. If that wasn't the case, ALL cars would be purchased in states with no sales tax. Well, at least I would do that.