Seems like the lack of an actual barrel would make it very wasteful as far as muzzle velocity - could probably obtain similar/better power with a tamer round and a bit of barrel to make use of the expanding gasses. A .357 magnum comes out of a revolver at about 1280 fps. Put it in a carbine with a 16” barrel and it comes out at over 1800 fps.
Your specific knowledge of firearms proves you are psychologically unqualified to critique this writer’s opinion. ;-D