I use the "set effect" command to make the moons of the Sol system habitable (instead of just resource nodes). But, I noticed that even after terraforming Titan (Saturn moon), it didn't lose the Methane Atmosphere trait even though it was not a Continental-type world (moon).

Additionally, I set nearly all of these moons to Frigid, but again after terraforming they've kept the Frigid World habitability value.

Suggestion:

When celestial bodies are terraformed they should have a randomly selected subclass appropriate for the terraformed class; ie a Tundra terraform wouldn't give you a Swamp subclass, but would give you a Taiga subclass.