Debut members were informed they have been chosen to debut from the start of the show, and had signed separate contracts from the rest.
At least with Produce 101, the trainees didn't actually know they were rigged in but the way I see it, no matter how much I like this group, the girls knew and profited from other girls being scammed, cheated out of their dreams and didn't have a problem with stealing someone's position if that meant their own dreams would come true. I can never see myself supporting a group like that ever again. No wonder knetz want them to disband.