To be able to better hear the cracks. I wonder if them there paddles/beaters/dividers really need to be that high as to make such a racket that hearing the crack is impeded? Maybe a drum with much lower protrusions would be ok. Beans tumbling make such a noise, if tumbled with less vigour the noise would be far less and the beans would still tumble and not slide due to rotation of the drum.
So, after not being satisfied with supposedly dark (9-10 on the ratings) and finding most are really 6-7. Very rare to see any oil at all. So I went the whole hog (it was just a matter of time) and bought a Aillio Bullet R2 Pro roaster and now am several batches in and finally have fantastic espresso! I've only started so have lots to learn about controlling the roast and different beans and how to blend them. But so far this is the one single thing that has got me closer to coffee nirvana!