Aboriginal Australia does not sort animals into sacred and ordinary. The emu is an ancestral being with Dreaming tracks running across country, it is a subject of ceremony and of restricted knowledge, and it is a large bird that people hunt and eat. All three at once, without contradiction.
What that produces is rules rather than reverence. Who may hunt an emu, who may eat which part, who may tell which portion of the story and to whom, and in which country a given account holds: these are the substance of the relationship. A man may be responsible for a stretch of emu Dreaming, which means he holds the songs and the designs for it and has obligations to the people whose country it crosses.
Emu imagery is everywhere in the art, from the engravings of the Sydney sandstone to the bark painting of Arnhem Land to the acrylic painting of the Western Desert, where an emu track is a standard element of the visual vocabulary and reads as the bird itself.
The general point matters more than the particular one. Australian traditions are many, not one, and a statement of the form "Aboriginal people believe" is almost always false. The emu is a rare case of something read broadly across the continent, and even there the local accounts differ, which is why this article says what the emu does rather than what it means.