Unlocking new game-characters seems to work bit illogical way.
At the moment it works something like this:
Releasing 7 prisoners (from either world, combining prisoners from two different worlds is not possible!) earns the player a new character, the new character is unlocked from both worlds.

The illogical part being that prisoners are not combined, but the unlocked characters are?

Is this the way it should be, or is there a bug somewhere?

Maybe more logical approach would be that either both would be combined, or neither?