No Dogma at all
The only "doubtful" would be the gas sucked out this cavity,(bell), as per your suggestion, not passing thru a layer of glowing charcoal.
Using a "blast" effect, to keep the glowing charcoal touching the nozzle tip is , per se, a good idea, but is it feasible ?
Looking into the perspective of a piece of glowing charcoal, then the surface getting in contact with the O molecules, is way far hotter then the rest of the piece. actually it nears the 3000 degree celcius, be it short time, per molecule. The radiation heat will make the environment hot and the carbon will absorb the biggest part of it in the transition to become gas.
Carbon will stay carbon until its oxydised with O, or sublimate if its above 4000 degree's Celcius.
I am using very high silica content materials, where as silica vitrify's at 2800 dergree celcius or above.
looking at the clumps of molten lava inside my gasifiers, its easy to see where the blast pushes the vitrified silica.
Even having a cavity, where the nozzle is free from contact, should not change the need for the gas passing thru a layer of glowing Carbon, for the reduction, never to forget dough that the blast is created by the suction/vacuum from an engine/blower.
The vacuum point is the part where as we should avoid to get non reduced volatile matter or Co2.