Re: not yours
"...But to claim that it gives you the right to make another copy of whatever work happens to be on that disc - is pretty much the opposite of how copyright works."
Or rather: if an owner of physical media loses that media and its associated backups accidentally e.g. tidal wave, volcano eruption and the like, then why shouldn't they be at liberty to download what they can of it?
Or even if the owner still has the original media intact, downloading it again from the interwebs is hardly copyright theft.
After all, it's not like they haven't paid (enough) already...