The names are irrelevant. Have the second richest city on an island swap duchies when its lord is appointed duke of a different duchy, and then listen to the outrage.
It's not ideal either way, I suppose. But at least the way it is now, you don't get things moving around unexpectedly. It is also the existing, known behavior. Changing it doesn't make it any more predictable, easier to understand, or consistent. It also makes for the creation of situations that were not desired and very difficult and inconvenient to undo. You may have to travel a bit now to take your region to a new duchy and *then* get appointed duke. But you also had the benefit of making an informed choice about what you wanted to do, and could easily have chosen to leave your region behind. Forcing the region change unexpectedly and unwanted and then forcing people to deal with how to get it back is decidedly worse behavior.
