My R1 experience that you asked:
The ADCOM interview was centred around the essays. Asked for more examples than what was mentioned in the essay to see a pattern of behavior. Sought precision clarity on personal objectives and how MIT can be of help. Questions on conflict management, team and leadership styles.
Subsequent interview with program director was finer details on the discussion with ADCOM member. Questions on fitment, clarity, two way benefit to the individual and cohort, short & mid term. Just be yourself and speak out naturally.
There are at least 20 more who have already been given final offer. However, they seem not to be very active in this forum.
Hope this helps.
Cheers and all the best
Saurabh