Orphan branch not well-defined?

Team,

Recently I tried creating an orphan branch in an existing repo using git-checkout and git-switch. 

Both commands have an --orphan option.

The results were different:

git checkout --orphan <newbranch> retained the entire working tree, including subdirectories and their contents.

git switch --orphan <newbranch> retained subdirectories but NOT their content.

Leaving aside the question of whether or not this is a bug, there doesn't appear to be any formal definition of the term "orphan branch" in the git documentation. Am I missing something?

Thanks, Craig