Elephant birds: Who killed the largest birds that ever lived?

As far as I can see from the article the "birds" were of the ostrich kind, not the flying kind we imagine when hearing the word "bird". As far as I know the modern science also says that many dinosaurs that didn't fly also had feathers. So why aren't the other dinosaurs considered "elephant birds" while this creature is?

More info <a href="http:&#x2F;&#x2F;www.sciencemag.org&#x2F;news&#x2F;2018&#x2F;09&#x2F;new-find-clears-madagascar-s-first-settlers-wiping-out-world-s-largest-bird" rel="nofollow">http:&#x2F;&#x2F;www.sciencemag.org&#x2F;news&#x2F;2018&#x2F;09&#x2F;new-find-clears-madag...</a><p>Paper <a href="http:&#x2F;&#x2F;advances.sciencemag.org&#x2F;content&#x2F;advances&#x2F;4&#x2F;9&#x2F;eaat6925.full.pdf" rel="nofollow">http:&#x2F;&#x2F;advances.sciencemag.org&#x2F;content&#x2F;advances&#x2F;4&#x2F;9&#x2F;eaat6925...</a>

Were these birds bigger than dinosaurs?<p><a href="https:&#x2F;&#x2F;blogs.scientificamerican.com&#x2F;tetrapod-zoology&#x2F;the-birds-are-not-dinosaurs-movement&#x2F;" rel="nofollow">https:&#x2F;&#x2F;blogs.scientificamerican.com&#x2F;tetrapod-zoology&#x2F;the-bi...</a>

Any DNA?<p>Might these be recent enough to bring back?

The illustration doesn&#x27;t seem plausible. Their wings would have to look far more bulky to be wide enough to lift their weight.