Extended attributes (xattrs) and alternate data streams (ADS) are different things, although they are related. So far, there is NO support for alternate data streams yet, although its work in progress: Back up and restore Windows Alternate Data Streams by aneesh-n · Pull Request #4614 · restic/restic · GitHub .
Extended attributes in Windows are currently primarily used by WSL as a way to store Unix extended attributes on NTFS (yes NTFS supports both ADS and xattrs). They are used to mark downloaded files or specify special file permissions.