Oh, interesting 🤔 I wonder if alien generation was just a problem for my custom walkbys then? It may work fine for you in that case.
Edit: it looks like Home Regions does impact my NPCs spawning, but this mostly impacts the Conspiracy Hub. Kuttoe did add instructions on how to opt-out certain sims, so I'm looking into that now. In the meantime, I'd recommend using the "International Lot" lot trait if using the Conspiracy Hub or Mysterious Skies.