How Come Trundle Doesn't Activate Battle For Freljord Against an Enemy Lissandra?

>From his lore; When Trundle returned to the warband, his fellow trolls bowed to his conquest. Calling his weapon "Boneshiver," he took a moment to enjoy the look of numb shock on his chieftain's face before he caved it in. Seizing command, Trundle announced that there would no longer be chieftains - only a Troll King before whom all of his kind would kneel. The trolls rallied behind their brash, new leader and prepared for the coming war. With Trundle leading the charge, the time of the trolls had finally come.

Its also been said that Trundle and Lissandra have a shaky relationship in which both of them are plotting to betray the other, so that makes me wonder why this isn't a thing to begin with? I feel like this would be a cool in character thing for him to activate if provided scenario happens in game.

Trundle has successfully betrayed Lissandra! The Frejlord is for the trolls now!