"Dead" in James means useless, not being used, inoperative.
A dead body is still there, it was never non-existent.
I think we need to be logical.
If a person has faith, but they do not have works, this does not mean that their faith does not exist, or that it never existed.
No, the incorruptible seed is still there, even though the works are not.
But in such a situation, faith is not accomplishing the purpose and goal which God intended for it.
The faith is dead. The absence of works is not allowing the faith to carry out God’s plan and purposes in the world.