MellerAM, I bought some ribs similiar to what you are describing a few years ago and the butcher told me when I bought them they were from older hogs, larger bones and stringier-tuffer meat. I bought them anyway, found them to not have the fat content of the smaller ribs. Cooked them 3-2-1, cooled, sliced, placed in roaster oven and took to work to reheat the next day for dinner. They were fair at best, tuff and stringy and wouldn't release from the bones. Haven't bought any big slabs since.
Hope you have good luck with yours and keep us informed.