>
> It should be "utf-8", in lower case.  How come it's in upper case on
> your system?
>
> Did you produce the Info files yourself, or did they come with some
> package built elsewhere?
>

I used homebrew to build Emacs, so I believe the info files were generated
locally during the build process, but I didn't do anything special in that
regard.

I've been trying out two different build formulas,
1. https://github.com/d12frosted/homebrew-emacs-plus
    (just GNU Emacs with some build options)
2. https://github.com/railwaycat/homebrew-emacsmacport
    (GNU Emacs with some source code modifications for OSX)

Both builds have the uppercase "UTF-8" local variable in their info files,
and both exhibit the behavior I described.