If something doesn’t have a functioning detonator, it’s not a real bomb.
Indeed, I suspect the perp’s defense will be it was just a clock. (The Achmed Defense.)
It is an issue of fact.
And, missing both a detonator to initiate the explosion or, from all that I can tell, the lack of an actual explosive "main charge" [rumors are that it was sulfur powder- which is not an explosive], and further having a clock that has no alarm function to switch power to detonate the detonator, and further having no stored electrical energy (battery or capacitive discharge system) to be switched by the non-existent, the facts appear to be that this was utterly and totally a hoax, e.g. a fake bomb.
Calling it a real bomb is like calling a pistol shaped piece of wood with a hole bored out in the fake muzzle and filled with ground black-pepper a real handgun. It's still fake even if I pack the fake black powder with bird-shot.
I certainly do not agree -- the mere lack of a detonator would not make me think a mass of explosives and nails mailed to my house was not a bomb.
But, oddly enough, the Federal Government took a position very like that, before the United States Supreme Court no less. In United States v. Western Pacific R. Co., 352 U.S. 59 (1956) the Feds argued that napalm bombs, without detonators and bursting charges, were merely barrels of gasoline, for which railroads were paid a low rate for transporting, and not incendiary bombs, for which railroads received a much higher freight rate.