Wasn’t gastornis a herbivore, then it makes more scence they add titanis or something as the epic terror bird. And then maybe an animation set with moas and then add gastornis in there.
Yeah, Gastornis isn’t a part of the phorusrhacidae family, so doesn’t count as a true ‘terror bird’.
Plus, best evidence indicates a herbivorous lifestyle. Although, that doesn’t mean it couldn’t have been dangerous. The cassowary is a herbivore and it’ll go right through ya!