@saddestrobots well, I think that the people that are going to run a PbtA game are probably, by and large, more adept at improvisation in that realm than the people that they are statistically most likely to be running a PbtA game for, people who only play 5e but want to check out that Avatar game their friend kickstarted. For that reason, I understand weighting the writing towards fleshing out successful outcomes, which are more player involved.