All I can tell you is this, if I click create new household to move in, I'm taken to CAS, there'll be the vanilla sim there waiting for me, I then click the light bulb to pull up my custom sims, I pick that custom sim, then I'm given the choice to merge or replace, I always go with replace, and once in awhile I'll get this, "this content was made with blah blah", and it'll show the Sim, usually bald, but the check mark on the bottom right will be greyed out and I will not be able to proceed until I delete that sim and create or add another. Could be an update and not an expansion, I rarely update the game. Their updates fix one thing then break 4 more.. typical Maxis bs.