If I understand what you wrote, there's a douga 
and a genga for every cel. I don't think so.

To me, gengas are drawings made to have a first 
global idea of what the scene is gonna look like. 
Like the first sketch to the future key cels.

I have here 3 gengas (Anime Taro called them that 
way !!) that are numbered A1-A2-A3. They don't 
look like the first 3 cels of the sequence, but 
rather like its 3 key cels:

http://perso.club-internet.fr/olazzari/camus.htm

I don't think that the guys who draw the dougas 
don't create anything since there's not a genga 
for every cel. Those guys are the in-betweeners !!