Yes, it does appear that the balconies from about the rear 20% of the ship do have larger balconies. I doubt this is an error. In fact - the same is true at th front of the ship, but I would book the rear for a smoother ride.
We stayed in a cabin forward of the penthouses and the ba;lconies were sized just fine, however. We were able to get a dining table out there and enjoy a great lobster dinner brought to us by our butler.