Hunter only did that for boats were they had a export order, or at least an intent.
From an owners perspective, I would not put ANY weight on that rating. If your cruiser is over 30 feet, its A. At 30 feet it can be close, A or B, but would that really make you feel any better if it was A? The rating is mostly a function of length. There are big A rated boats that I would not step foot on, let along cross an ocean on.