Well, thats how the industry uses the term; a 1.78 (16x9) image is called anamorphic for the simple reason that not calling it such implies a letterboxed image. The anamorphicness comes from the dual encoding for 4x3 TV's i believe, since the image will be squished to fill-by-letterbox or stretch to fill-by-fullframe depending on your TV. I think. Its a bit confusing.

Regarding the previous post I made about the poor resolution of HD and the prequels--it should be noted that the prequel films arent actually HD res. They are in fact, less than HD resolution--because HD resolution is in a 1.78 native ratio. The 2:35 aspect ratio is achieved by cropping. So, in fact, its a blow-up of a smaller portion of the image.