Nah, just a realist with a couple of engineering degrees. If we all drove 45 mph, we'd get far better mileage across the board, but driving would be a lot less enjoyable. Also, 43 mph is nearly the ideal speed for maximizing mileage. You are likely too young to remember when the national speed limit was dropped to 55 mph in order to conserve fuel. Boy, those were the good old days....
Having just returned from Bonneville last night, let's just say it takes a lot of hp to reach 200+ mph. Speed kills mileage and your 0-45mph example is not representative of "normal" driving. 20-21 mpg seems to be closer to the average so far. Far less than the once "up to 27 mpg" and still 10% below the 23 mpg updated number Toyota is advertising. Certainly better than my wife's 100, but my 3.9L Isuzu (diesel) powered 80 series gets 20 mpg and it's rolling 35's with about 7 inches of lift. Not too bad for a 35 year old engine....and when the compound turbos spool, it sounds really cool.
At the end of the day, I'd still opt for the smoother GX engine now that I've driven both, even with the 2 mpg decrease in mileage.