Not to make matters worse, but more give an idea of what might be happening (because I would want this myself):
I got an interview invite late Sunday night, and there was only one day left of interviews (this Friday, which made for the most expensive plane ticket ever). This made me assume that I barely squeaked my way in there and that might be one of the last wave of interviews to go out since there was only one day left as to when you could interview on campus.
This is no scientific thinking, but wanted to let you know my thought process and give a bit of transparency.