Interesting point!
I used a helmholtz coil in physics class last year, in the middle was a helium bulb with an electron gun inside, and the coils would make the electrons from the gun spin in a circle, and you could control the radius of the circle from the applied voltage, and we calculated the velocity of the electron.
I noticed that in stans gas gun the outer SS tube would act as the 'core' for the VIC built in, and you are right, the gasses do go through the magnetiic field as well. Now to think about this, the effect would be that the magnetic field of the VIC would be pulsing in a unipolar direction, most likely in the direction of bottom to top of the gas gun, pushing the gas through.
This could be for efficiency, not requiring a pump... as it acts like a magnetic particle accelerator as used in the EPG. This would also have the effect that the moving hydrogen and oxygen, as magnetic particles, would up the voltage of the secondary/chokes which I assume are wound at the top of the gas gun, with the primary at the bottom. This would also force stray electrons upwards with the magnetic field to the collection grid.
