May be it has a Dummy display barrel in it !
My understanding is that would make no difference. This is supposed to be a pistol. There is a stock attached. Unless this is a rifle and has a 16" barrel, dummy or not, this would be an unregistered SBR. As I recall the statute lists barrel length, but there is no mention of whether that barrel is live, demilled, or a dummy barrel. It simply states barrel length. So a short dummy barrel is still a short barrel because this is a firearm, not a dummy firearm.
It would seem to me that any dealer would alert the BATF&E as soon as they opened the box. As a dealer, the BATF&E could show up about another matter unannounced. Or Someone has already clued in the BATF&E about this and are tracking it down. So I would think if the dealer received the package containing this and didn't call, they could have their own legal entanglements. YMMV.
Scott