[dmurray]

> I suspect that using sorghum for fermentation really means using whatever wild yeast happened to be on the sorghum, and the results too variable to regulate for commercial sale or export.

Definitely this. Sorghum is not a "fermenting agent": it's not an organism that eats sugars and shits out alcohol and carbon dioxide (actually, it's pretty much the opposite). It's just somewhere wild yeast likes to live.