I do use retired climbing rope for my double line reefing setup, on both 1st and 2nd reef points. Although it does stretch a bit, when you winch it tight, the reef points certainly stay where they are supposed to. So, in my experience, the stretch is not a problem. The strength / size of the line is likely way overkill for a reef line, but free is free, and it works fine.
I also have used it in the past, to tightly tie down a tarp over the boat, when stored outside for the winter.