shouldn't there be a new category for the versions that go into the negative layers?

As a current SSG WR holder, the extra layers are often not a major disadvantage because of the new cave terrain gen and addition of moss. Although I can't speak for RSG with as much confidence, We've completed a very rough 1.20.1 RSG Duos run in ~1:30:00 that we could probably cut in half so I don't think it's unreasonable to leave them in the same category. Good question though, we asked that as well before we started.

i think it should be a new category, cuz it ads a whole new aproach to the RSG cuz deepslate is a pain to mine

You shouldn't be mining deepslate, you should be turning it into moss and hoeing it. I still think the categories should be split though because they have different approaches.