Mostly right. They changed being forced to stay there being only able to see her on weekends. Now it's an extra thing you can do like a subjugation. That change is basically why we had to wait 6 months.I think DLC is more focused on post game.
Correct me if i am wrong.
DLC happens after hot springs quest.
You and other members stay at hot spring where most new events will happen.
Your sister stays at home and you can visit her.
Some things will be added to pre hot spring quest content , but most content will be after hot spring quest.