Not for population. Sizes 1-3 are celestial bodies smaller than 2000km. So moons like Iapetus and large asteroids. They physically cannot house populations larger than "tens of thousands" due to small size, as far as the tables are concerned. The section on population does state that with right technology, even inhospitable worlds can house large populations. I guess they draw the line at millions of people living inside a hollowed out asteroid. But like everything, the table results only give a broad, high-level view of the world. Results can be ignored or changed to as you see fit.