So what makes this recipe so great, is it the corn meal and the potato that make the difference, or the concentrated juice? Or is it something else?
Muscadine wines certainly have a unique taste. I discovered it Christmas two years ago, there were three seasonal varities that the Duplin vineyard produced, and they were an instant hit with my wife and our neighbors. The local wine and spirt shop couldn't keep it in stock, we kept clearing their shelves. Now I order by the case, right from Duplin.
Muscadines are commercially grown but may be hard to find at a reasonable price outside the regions where they are endemic. I would say muscadine wines have unique tastes, since there are so many versions of them made. Each winery has its own ideas.
To answer your question about what makes this recipe so great, to me:
1.) My version is an adaptation of an old, old country recipe that has been used for many years. (The original recipe is here as it was given to me, too, if you want to try it.) To me, the adaptation is the best of both worlds - old and new winemaking techniques. Chiefly the back end of the process is modified, resulting in a clear wine from using modern techniques. The wine is also drier than the original recipe would be, allowing for more adjustment to taste on the back. The original recipe will be very sweet when done.
2.) Using RC212 means using a far superior yeast for extraction than bread yeast or natural fermentation, the way it was done originally.
3.) The baking soda in the self-rising corn meal does something for the wine. It buffers the acids. The potato is there as yeast nutrient, as is the corn in the meal. I like how old-timey that is.
4.) It is an all-juice recipe the way I adapted it. That makes a tremendous difference.
5.) If you follow my adaptation closely, your will get the wine off the lees quickly in a two-stage initial secondary process. That clears it better and helps with any "foxiness" in taste that muscadines are sometimes maligned for by wine "experts."
6.) They are powerful lil grapes! See
http://www.livestrong.com/article/238659-health-benefits-of-muscadine-grapes/
Hope you find some muscadine or scuppernog grapes. If not, you can adapt the recipe for use with Norton (another American grape variety), or even concord or other red grapes.