I’m not entirely sure how Therizinosaurus multiensis stays populated on the island. It is surprisingly slow for its size, and is a solitary creature (so no pack to back it up). I suppose the fact that its sheer power rivals Tyrannosaurus is the only thing that allows this very aggressive medium-sized herbivore to thrive on the island.
A tamed Therizinosaurus is one of the most versatile mounts a survivor can have. It can be trained to use its claws brutally or delicately, allowing the rider to primarily harvest the specific kinds of resource that he or she needs, with abnormally extreme efficiency. And in combat, these same claws can pierce straight through the toughest armor. This flexibility more than makes up for its inability to carry the large loads of the island's many herbivorous pack beasts.
The claws of Therizinosaurus are some of the most versatile biological tools I’ve encountered, as adept at removing trees and foliage from Therizinosaurus’ path as they are at piercing the thick shells and hide of the island’s most defensive creatures if backed into a fight.