Zul'jin the legendary warlord of the Amani Trolls before, during and after the Second War, up until his premature death in the Burning Crusade, was well-known for his tenacity, cunning, dangerosity as a fighter and burning hatred of the elves of Quel'thalas. But there is also a detail that made him distinct from most other trolls, it's that he had lost his left arm and it never grew back despite the trolls having the ability to grow their amputated limbs back.
Why did Zul'jin never regenerate his lost arm despite his racial ability ? Was it because of some magic, similar to Trol'kalar's power, or did he refuse to grow his lost limb back ?