Why does casting Lux's shield cause her to throw her wand?

If you throw your Lux W in the direction of a Braum that has his E up, it will not explode when it hits him. However, his E states that while it is up, he intercepts projectiles and causes them to explode.

Your W (nor your wand) doesn't explode, however, even though it obviously should. It just goes through him and comes back as normal. Well, if it isn't a projectile, what is it? That doesn't really matter. What we do know is it does not project because it can't.

If it can't project, it cannot move, so how is she able to throw it? Or does Braum's E just have a lying tooltip like pretty much every other tooltip these days?