[mannykannot]

I suspect there are two issues here put together in a possibly misleading way: 1) it is not surprising that the juvenile Gorgosaurus would have fed on the smaller animals, for fairly obvious reasons that have nothing to do with what the adults would have fed on; 2) the small animals would not be an adequate diet for adults.

If this is the case, then it seems odd for the latter to be used as a justification for the former, but when people are talking extemporaneously, it is not uncommon for them to jump from one topic to another without completing the former.

As an example of how larger predators often ignore small prey, consider how some hummingbird species seek out nesting sites close to those of hawks:

https://www.audubon.org/news/why-hawk-hummingbirds-best-frie...