In my experience, programs don't send rejections until their cohort is fully secured. That way, if all of their finalists somehow all decide not to go, they're able to go back to the "semi-finalist" pile (often which you don't know if you ever are, only two schools I know of tell people) and restart the interview process. They'd rather not reject anyone and then have to reach out and be like... "heyyyyyy jkkkkkkkkk"