I think when philosophers speak of moral realism or objective morality, they mean that there are moral propositions that are objectively true, but that doesn't necessarily mean that we (or other animals) know those objective moral truths yet. Rather, we get through ethical reasoning better and better approximations of them, similarly to how scientific theories become better and better approximations of the laws of nature. That's how I understand them anyway.
Well, just don't ask me whether I agree with this view or not. I know some r/badphilosophy asshole is probably going to lampoon me for this, but I just can't get myself to care. There are so much more concrete, interesting, more certain and enlightening things to say about morality, so I'm more interested in those.