I don't see the issue here. Some filesystems store data in several streams, and have been doing so for decades. GNU tar gives warnings about stuff it doesn't kn

I don't see the issue here. Some filesystems store data in several streams, and have been doing so for decades. GNU tar gives warnings about stuff it doesn't know, and which can be ignored without a problem. If you haven't ever seen a different *nix system than Linux, this may be a surprise, but it should be taken as an opportunity to learn something new and move on.