`git rev-parse --git-dir` relative to current working directory?

So, `git help rev-parse` [mentions the following][rev-parse], as of 2.8.0:

    --git-dir
       Show $GIT_DIR if defined. Otherwise show the path to the .git
       directory. The path shown, when relative, is relative to the
       current working directory.

However, when inside a symlinked repository, this doesn't function as advertised:

    $ ln -s a-symlink a-git-repo
    $ cd a-symlink/.git/hooks
    $ git rev-parse --git-dir
    /Users/ec/Documents/a-git-repo/.git

From my reading of that snippet of documentation (“The path shown ... is relative to the CWD”), I'd expect to receive `..`, not `/absolute/path/to/a-git-repo/.git`.

Is the documentation incorrect, or is this a bug? (I'm hoping the latter: I'm trying to write git-scripting that is sensitive to symlinks, i.e. retains the user's CWD without unintentionally resolving symlinks in their path during operation; and it'd be ideal if this were handled as documented, saving me manual effort checking symlinks.)

⁓ ELLIOTTCABLE — fly safe.
  http://ell.io/tt

   [rev-parse]:
<https://git-scm.com/docs/git-rev-parse/2.8.0#_options_for_files>
      "git rev-parse documentation @2.8.0"