The differencies are not so dramatic, if you keep the “blow through” area on the grate near matching the restriction area and the reduction volume less than the oxidation volume.
Using one dimension of tube from the nozzle-roots down to the ash-pan.
This type of flow will be rather swift whole the way trough.
It usually blows it free of ash after a while on idle when giving full throttle.
In GMR Imberts the grate area is as wide as the outer shell. It has very slow gas streaming through it; part of the gas never goes through it at all.
In this case shaking or sieving has its clear place. Without it, burn through from the restriction downwards or sideways is common. Too much shaking causes side-blowing as well…