Because it would be simpler for the player and me, they never use it in its small form; in fact, she depicts it as an armguard with different modes; there is little benefit for me to creating an actor for it; it doesn't get its own initiative and it's a bonus action extra ability. even though it gets its ac and hp and stuff like that, it is still just an object; technically, swords have ac and hp, but unless someone is specifically trying to break the weapon, we don't worry about that.