You're ignoring CAFE impacts where a few tenths of one MPG can have a big effect. If it had no effect then Ford wouldn't be using them.
The PCM will maintain proper engine temp by opening the shutters all the way or part of the way so it's not going to have any impact to engine cooling either.
The impact is small and as Waldo points out isn't worth the cost on some models so that's why it only shows up on certain models and certain vehicles.