That's a pretty big jump between Ceres' small but still significant gravity and being in total freefall. Granted, Ceres is pretty tiny compared to Mars or even the Moon, but we don't know at what point on the spectrum between "microgravity" and "Earth" do we see noticeable health risks. Maybe we're finely tuned for Earth gravity, and we'll suffer even on Mars. Maybe it's just the freefall that's the most harmful, and that any gravitational sense of "down" will be healthy enough for a settlement to actually be viable. Some long-term lunar habitability experiments would be a good first step to finding that point.
If asteroid mining starts to catch on, Ceres would be a really nice spot for staging mining expeditions, materials processing, etc. Combined with the abundance of water ice, it could be even more ideal of a colonization target than even Mars, especially if the effects of longterm exposure to its lower gravity can be identified.