Got the call to schedule my interview today! II received 2/19 and the person had multiple options for next week and the week after. They called from a 201 number just before 5pm EST.
I'll add another datapoint to this info session mess: in my original 2/19 II, I did get the "and are required" part. When I confirmed my II, the confirmation email did say the student affairs session was encouraged, but didn't explicitly say required.
I did get, however, an email today about how there's one final student affairs info session on 3/13. It said "If you have not already joined one of these sessions, please register for the event."
I'm not sure about anyone else but from the communication I've gotten, I'm playing it safe by attending the student affairs session. I intend on going to the admissions day and interview (duh), the student affairs session, and the student Q+A (although I don't think the last is mandatory- my interview is just on the same day and I figured I may as well attend both). I hope this helps!