Fortress walls being destroyed by enhanced flame ability

The new ability to destroy the hive walls is meant to remove the walls. It goes away at wave 4 so make way for other abilities that can be used while leaving the walls up.
BUT When you used the Enchanced Flame skill, it destroys the walls even if it's picked up after wave 4, making either the walls or that skill useless for those who want to keep the walls (Melee)