It is inert. Isn’t that like dropping a rock? What’s to study?
At a guess: accuracy of the weapon ballistics dialed into the bombing/targeting software of the carrying aircraft. Penetraion tests as well, if that variant of bomb.
It has the exact duplicate of a live weapon except for the warhead, where an inert object with the same mass and balance is inserted instead.
They are studying the weapon’s ballistic characteristics so that, God forbid, if they have to use one, it will hit the target the pilot aims at.