"We are aboard, humans, and elites. Will you not come with us brother?" He didn't say Humans and Covenant. And the Post Halo 2 part of GoO was still in the earliest stages of the Great Schism. During that time, yes, Sangheili used Hunters and Grunts as Arbiter did in Halo 2. However, there is no proof that during Halo 3 it was anything more than Elites allied with humanity. And if there were more species, it had to be such a negligible amount that they didn't get mentioned in and "during halo 3 lore"