I'm not sure it was a deliberate change, but more lack of knowledge. As much as I am enjoying Duggan's run so far (especially after the years of trash from Bendis), there are small continuity discrepancies like this that bother me. It just seems like he's trying to stay true to established continuity, but isn't as big a continuity buff as some of us would like.
Massive continuity oversights are keeping me from fully enjoying Lemire's Thanos, too. While the story is pretty good, I just can't get past Titan still being destroyed, as established by Jason Aaron in his Thanos Rising series.
Ah well, at least cosmic Marvel is making somewhat of a comeback. Al Ewing is absolutely killing it with Royals and Ultimates. Now that dude knows his continuity.
True. They are currently functioning under the premise that Titan society is fully functioning underground that the ruins remain on the surface. Of course, this is a clear retcon/revamp since there are past issues that show Titan society functioning on the surface (spaceships are shown looking down on them).
And yes, Ewing is knocking both books out of the park. He is now my current favorite writer and should be the one leading Marvel's cosmics.