He's immature because he's essentially forcing her to become his mate, it's not because he doesn't want her to have other males even Curtis didn't want that, it's the expected reaction. He just acts like a manchild
That's right he's immature and childish but that's explain everything since he's mostly likely the youngest among Bai's males, so what are you all expecting too? I'm just saying it since some readers are only looking out for his flaws though