Gordon Rowley has divied genus Haworthia in three separated genera.
Haworthia - remains same (includes subgenus Haworthia)
Haworthiopsis - previously subgenus Hexangulares - but it seems that species like H. viscosa, H. venosa, H. pungens, H. granulata are moved to new genus Tulista.
Tulista - previously subgenus Robustipedunculares, several species from old Hexangulares (as mentioned above). What is new is the fact, that Rowley includes under Tulista genus Astroloba, Poellnitzia and Aloe aristata.
I do not have much further and more detailed informations. But I will try to find it out for you. First two make sense, the very strenge mix in Genus Tulista is very problematic.