I’m not sure about the iscsi protocol. They allow VMs, including harddrives via USB, so the point of doing this making it more expensive does not apply considering someone could just hook up 100tb+ of USB drives and still be clear under the TOS.
If they did have a problem with this I would just do that instead.
And the situation where I need to restore more then 8tb would be when I lost all my original data, and the backup NAS itself.
If that happens I’m not worrying about spending $280.