User blog comment:Kogath/Monster Hunter X Discussion/@comment-5716529-20151114193326/@comment-25275196-20151115013919

I could see no G rank working if just more content was put into the other two ranks. Anyway, it's all but confirmed that the HC variants are beyond High rank difficulty, if they are classified into a different catergory and their equipment is given a unique rarity. So even if there's no G rank, the HC monsters will provide plenty of data.

Also, Subspecies still haven't been confirmed yet. Maybe that's where the missing 1GB is going.