MMI not the first to know a few years ago
When my DS went to MMI a few years back, the first party notified was the nomination source (MOC) that the appointment was allocated to and the school was not notified, even though my DS had gotten a ROTC nomination from the PMS at MMI.
I could possibly see that if the nomination was allocated to the PMS for a ROTC nomination then perhaps the PMS would get notification and possibly be allowed to inform the cadet candidate of the appointment, just a guess, so unless things have changed then MMI is not the first to know (wasn’t then anyway).
You could contact MMI and ask them what the historic behavior has been regarding if/when they get specific notification of their cadets getting appointments from any SA, too.