Not to be too annoying, but that file is how it supports the feature on non-posix-compliant file systems (usually FAT). On filesystems that support file-streams (or the original HFS), that metadata is stored on the file itself
Considering how pushy Apple normally are when it comes to forcing their customers to use new things so they can obselete old ones, I am very surprised where Apple have drawn the line in supporting older systems.
