As far as I know, the debug panel (if it's still in the code) isn't hooked up to anything in either version of AI CS6, and it didn't do much of anything in CS5/5.1 either.
There is a plug-in called Path Area that works in CS2-CS5.1, but not in CS6 (I just tested). If you have CS5 still installed you can run it, otherwise you might check with the telegraphics.com.au folks if anyone might update it. (I see it's referenced on the site you linked in your question.) There have been some pretty massive code changes under the hood in CS6, so 3rd Party "casual" plug-ins like this are likely casualties of that process.
James Talmage ("JET" on the Adobe Forums) had a great script that would do this, but I don't have it and his site is clearly in some kind of rebuild or state of neglect. Links to it that used to work no longer do.