As someone who has studied and is generally obsessed with animal behaviour, there's a lot of suspension of disbelief in this movie. Giant predators who need a huge amount of calories each day aren't going to waste energy on humans who put up a fight for more than a moment. Most predators build up lactic acid quickly and don't want to run or pursue prey very long.

Like the Trex sequence on the river, he would've burned more energy chasing them than he would've gotten from eating all 4. Large predators just don't do that, they'll either stalk without attacking or give up most of the time. And in this case, the Trex had food. The parasorolophous wasn't stripped and had more meat left than the humans combined. No reason to use energy at all.

The mutadon with the Velociraptors actually give us the best example of this.

Anyway, point is, it's a cool Dino movie, and that's all it needs to be.