I was using arbitrary in the sense of an individual whim.
I understood your intent, but I don't think that procedurally creating a game setting actually removes any "individual whim", it just moves those arbitrary decisions from the design of the setting to the design of the procedures (in this case, a game) that generates said setting. Since, in this case, we are talking about taking a setting that could never have happened historically, Twilight 2000, and advancing it forward in time with a vast list of unknowables such as the probability of habitable planets, the types and frequency of alien life, the detail of any sort of FTL travel, etc. It's whims stacked on top of whims.
However, that avoids the main issue here. What possible advantage is there of a setting being procedurally generated over one that is designed for a specific purpose and feel?