> My first instinct was, I had underspecified the location of the car. The model seems to assume the car is already at the car wash from the wording.

If the car is already at the car wash then you can't possibly drive it there. So how else could you possibly drive there? Drive a different car to the car wash? And then return with two cars how, exactly? By calling your wife? Driving it back 50m and walking there and driving the other one back 50m?

It's insane and no human would think you're making this proposal. So no, your question isn't underspecified. The model is just stupid.