While I don't have any experience with WSL, so I don't know that. What I do know is that restic, at least for now, does not backup or restore NTFS extended attributes and NTFS alternate data streams. On Windows, when run as a native Windows binary, it'll save folders and files (with the "content" of the files).

Adding alternate data streams would require modifying the repository format. And to be honest, I'm not convinced that it's worth the effort.

There is a similar feature to alternate data streams on macOS, called resource forks, which may include e.g compressed data if using HFS Plus Compressed, alternative icons for files...

A similar question can be raised about filesystem extended attributes, which on macOS may include hiding files via chflags(1) as well as hiding extensions via SetFile(1). Those are visible using ls -le@ (-e for ACLs, -@ for xattrs).

A possible extension to support alternate data streams, as well as other data (acl, permissions, attributes etc.) would be to use the windows backup api (see https://github.com/Microsoft/go-winio/blob/master/backup.go )
This would also enable backing up files without having permission to access them (from an elevated command, so it would be even possible to backup files that even the Administrator can not access, f.e. files only accessible to "LOCAL_SYSTEM")
However, this would need an extension to the repository format...
(I have no programming experience in go, otherwise I would probably hack together a POC. But maybe I try that as a project to learn go ;-) )
Further documentation of the API:
https://msdn.microsoft.com/en-gb/library/windows/desktop/aa362520(v=vs.85).aspx
https://msdn.microsoft.com/en-gb/library/windows/desktop/aa362509(v=vs.85).aspx