On the review/flags tab, "exact duplicate" flags include the URL but there's no option to close them as that URL in the Close dialog. Can we please have "same as flag" as an option, or put the flagger's suggestion in the "Other users chose..." section?
This was somewhere on my todo list to finish up, but (with your reminder) has now been completed (next build, at least). We already do the work to recognise "they're flagging it as a duplicate of [x]"; it was just the voting dialogue needed updating to include that data. Which is now done.