I basically agree with you. The description of the Stiletto pistol is real PhD level stuff!!!
The “rocket” bullet is unlikely to be more than a projectile containing the propellent so the gases do not have to accelerate down the barrel-the Langweiler “impuls-Antrieb” or impulse propulsion principle he published in June 1939 and the basis for the so called German “rocket” bullets. The Venturi (convergent/divergent) nozzle simply trades heat and pressure for exhaust gas velocity, and requires a VERY significant pressure drop across the nozzle to achieve supersonic velocity of the exhaust gas. A rocket can’t operate in an unported barrel because the exhaust gas pressurizes the barrel behind the projectile and prevents sonic flow in the throat of the nozzle.
All this is well and good, but Rocket Bullets will probably attract more attention than “impuls-propulsion” bullets.
More important to me is that I’d love to have some of these in my collection, regardless of whether they are real rockets or not. They are interesting examples of salesmanship/showmanship, probably rather than technological excellence. The Hornady Zombie loads are an excellent example of a success of salesmanship/showmanship!