Summary translation: The producers wanted Gen to submit a plot with overly brutal killings, and killing them off slowly taking 2-3 episodes...so Gen delivered with that in mind.
Exact translation of this excerpt: Q - So on that part there was this wish from the production side? Urobuchi - Yes. And I said "Clearly it would be too cruel to kill one character every episode. Let's kill them slowly using the span of 2 to 3 episodes." and so I proposed that plot. Then Shinbo....