I don't find that the cyclone design really cooks herbs unevenly.
Rather, that it causes some of the herbs to get stuck around the rim against the hot glass (where they are not directly in the airpath, even with the turbulence described by Steve), causing the hot air to have less contact with the herbs. This makes the draws notably thinner when using a small amount of herbs in the cyclone bowl IME (which seems to explain the notable difference when using the elbow pack method recommended by Steve, himself IIRC).
Overall, I feel that the design of the cyclone bowl is an excellent one (the way the hot air travels up through the herbs causing them to stir, the way the dome screen and the elbow both create turbulence and encourage the collection of particles that may get through the screen in the elbow itself, durability, manufacturing/purchase cost, ease-of-use/cleaning/refilling, black silicone to keep it cool for removal, etc.)
Nonetheless, with a small amount of herbs in the cyclone bowl, I notice that my draws seem thicker with a slightly elevated screen and that all of the herbs seem to jump around (rather than a small amount getting stuck around the rim against the hot glass). Additionally, the extra screen helps prevent any particles that would possibly fall through the screen and onto the heating element.
In conclusion, I don't feel that there is anything particularly "wrong" with the design of the cyclone bowl, but the elevated extra screen does seem to help improve the performance of the unit when using small amounts in the cyclone bowl itself (IME).
Maybe a rephrasing would help Steve understand better, or maybe he doesn't need to understand (as it is an easy mod and the elbow pack he, now, recommends also addresses this issue)?
I am sure that he could sell "cyclone bowl shrinkers" (which would simply be a bent piece of stainless steel wire) for $6 a pop, while not even having to recognize any performance difference. To each their own, though.
PS: I don't fill bags and my two screens are elevated by a layer of glass beads.