Here’s what Duke says about interviews:
“Your chances of admission won’t be affected adversely if we are unable to offer you an interview, nor will they be affected if you choose not to send an extra recommendation (in lieu of an interview).”
Basically, the interview doesn’t mean much if they can’t offer it to everyone and it won’t hurt you if you don’t do one. This leads me to believe that adcoms do not give alumni interview notes much thought and that the interview is as much about keeping alumni engaged with the college and giving their time/money than about evaluating applicants.
I always go back to colleges (especially ones with billion dollar endowments) are big businesses as much as they are altruistic beacons of higher learning.