Plot twist: They did not release any waists technically more powerful than Black Belt, instead they obsoleted it by putting it's primary reason for being powerful in large amounts onto every other gear peice we use anyway and not increasing the cap, so the primary reason for it's power was irellevant because we're always capped on haste no matter what.

What does this mean for the black belt? No idea, it just doesn't really fit into their explanation, regardless, who knew we wouldn't need haste on the belt slot anymore, when traditionally it was the belt's most important function.