EDIT: One more quick clarification/explanation: Citizen vs Subject - Imperial (polity) Citizens are above the usual population of the Imperium (polity). Through service or special privilege they have the trust of the Imperium to act in accordance with its desires and goals. This grants, among other things, freedom to travel throughout the Imperium. Subjects are generally limited to travel within their home system and that only on local transport.
So does that mean in TNE UWPs boneyards and dead worlds may still have a significant population of subjects but no citizens thus making any recovery operation hot. :devil:
The pop digit should be an all or nothing count of sentients on and around the main world. Other planets in system have there own UWP that you get when delving into the system. It's the main world that brings in the ships or not.