Gun in question.
Federal definition of shotgun in the law:
For the purpose of this chapter—
(d)Shotgun
The term “shotgun” means a weapon designed or redesigned, made or remade, and intended to be fired from the shoulder and designed or redesigned and made or remade to use the energy of the explosive in a fixed shotgun shell to fire through a smooth bore either a number of projectiles (ball shot) or a single projectile for each pull of the trigger, and shall include any such weapon which may be readily restored to fire a fixed shotgun shell
I don't how any 22 long rifle ammunition meets the definition of fixed shotgun shell including the 22 #12 shot cartridges made for years.
So my argument would be because this firearm is not a rifle or shotgun it simply has to be 26 inches or more in overall length to be legal (not an 'any other weapon') so it could be sold with a much shorter, handier barrel.
Currently its sold with a 36.5" overall length and 18.5" barrel.