Rag joint
Well if you open your hood, you won't see no rag joint . In 50 years, you're the first guy I ever heard call the coupler a rag joint, and think to remove and replace what ain't even there,lol. But if you got it off the net, I guess we should cut you some slack,lol.
To be fair, I think the other Mopar bodylines and pick-ups do have them. It's a cheap easy way to put a lil angularity in the shaft, and a lil vibration isolation at the same time. My guess is the A-bodies were just not worth spending the coin on. Plus if you look down in the darkness there, there really isn't any room for one.