You're right. I was thinking of dvdisaster. My mistake.
However, par2 is not a substitute for it, as without the kind of ECC that dvdisaster puts on the CD/DVD, the files on it might not even be readable, so the par2 files on it would themselves be inaccessible, making them worthless.
When I mentioned separating the recovery files, I meant "burn them on the media and also copy them somewhere else." I think par2 can pull data from a re-ripped iso even without, say, legible file names.
However, par2 is not a substitute for it, as without the kind of ECC that dvdisaster puts on the CD/DVD, the files on it might not even be readable, so the par2 files on it would themselves be inaccessible, making them worthless.