Does it mean that American graduate students were rejected without receiving an interview invitation from a real person?

Just because American graduate students didn't receive an interview invitation from a real person doesn't mean they were rejected.

Interviews in most universities are not a necessary procedure for admission.

Even if there is an interview notice, it is generally up to the applicant to choose the interview or not to accept the interview.

Interviewers are all nearby alumni, and the success of the interview has little to do with admission.