It means that like in DOS2, after Act 1 your party is fixed and cannot be changed.
But hey, "it's not DOS3!" ...
It just means that the story will be fixed and linear like in DOS. You will basically be on rails through the acts with "large" maps that you can explore, but not return to after you complete each act.
Last edited by qhristoff; 23/09/20 07:58 PM.