This is a correct unit for it. Why? Think of it like a tube where as you move along it you use up the fuel. Over a set distance you would use more in a lower efficiency vehicle. Since the length of that pipe is the same, then the change would be the area of the ends of the pipe. Thus fuel efficiency is an area, smaller is better.
That is just more propaganda. In the netflix program about it they show that they can’t tell the difference.
The whole natural diamond thing is they want to control the volume of diamonds on the market. If you can make them, then there will be such a high production the prices will plummet. The only reason the price is high, is that they keep production low.