"Don't over rely on your ability to see in the dark"
What a weird thing to throw out like that, it's like saying don't over rely on your eyes working.
While true it is something that should come up during training, and not focused on only the darkness part.
Two heads on an ax isn't useful and only makes it heavy.
He is strength based, heavy is what he needs, and having 2 blades helps with the balance.
But it really is comicly oversized xD But that is fantasy battles for you, can't rely on our understanding on how you should shape weapons when you can fight flying dinos by chocking them.