Supposedly Gabranth is mentioned as a Beastmaster of some sort too. My guess is an NPC brings it up, as i didn’t notice it just going through the Resistance story.

That aside BST doesn’t work as a normal job really. They could give it set monsters, make it more like Ranger or the like I suppose with actual animals, but otherwise I don’t see it working out. And if they did it would need a new weapon if it’s RDPS.