The texture on the ribs were great. No toughness at all.
If you check the ingredients, I think you’ll find the mustard you rubbed the ribs with has vinegar. It doesn’t take much to tenderize the meat, when it spends 8 hours simmering in it.
Ribs are usually OK, but things like roasts are tough when cook,in sous vide. Better to cook, in crock pot I find,personally) I’ve seen video,of folks taking tough cuts and coo,ing for long hours in sous vide and claiming it tenderize it enough to eat, but I’ve tried it a couple,times and not found that it helped much if any. Maybe I didn’t coo, long enough (have tried 12 and 16 hours)