Factual error: The deer in the forest somehow does not hear the giant dinosaur approaching, so doesn't run away. (01:21:10)
Suggested correction: A different interpretation is that the deer knows the difference in the sounds - gurgling/roars of an approaching herbivore versus carnivore - so it didn't perceive it as a threat until it got unusually close (so the deer looked to see why). The dinosaur flung the deer aside, then proceeded to eat the vegetation where the deer was. It isn't likely that the dinosaur (if a carnivore) would toss aside a fresh deer meat brunch in favor of some green brush.
The therizinosaurs were herbivores.