Hori, I think that's a bug due to the new patch. Due to the new settlements, tt's likely that most planets had their flora and fauna also rearranged, and I was in a planet almost getting all fauna, minerals and flora discovered. Due to the changes, I ended up with some off-by-one / by-two. That's my hypothesis. Usually, even if you try doing that for hours and hours, it's already nigh impossible to get 100% completion of discoveries on a planet.

Yeah, relatable :D I think only the 19 most "important" ones are objectives and then there are extra ones for diversity that are less important... but that's just a guess, I find the whole thing unintuitive, but ultimately, I don't really mind. I like discovering and naming as many things as possible, and this doesn't impede that.