Just curious how this works. I assume the SA is waiting to see if a competitive student receives a Nom. When the SA is notified by the MOC that student A is on the slate - is the MOC then given the option to notify them? (Some do and some don't) I'm assuming then the student doesn't even know they have a Nom yet? So the call from the MOC is telling them they have a Nom AND an appointment? That must be an exciting call! How fun to be working in the MOC's office and get to make that phone call.
Go to the NOMINATION forum here, and read the threads at the top about nominations. If you are curious about this piece. The Nomination piece of a SA is the same, no matter what SA you are talking about.
In a nutshell, the MOC provides their list (slate) of candidates they would like the SA to offer and charge their spot to. This process is completely separate from the admissions process of XX SA. The nomination is a requirement of being offered an appointment, the other pieces are being medically qualified, and academically qualified.
IF a candidate on a slate is deemed qualified by the SA, then the admissions process can begin (BTW...there is a whole lot of other stuff that happens here. As not every person on a slate, that is deemed qualified, is offered an appointment) of selecting who the SA wants to assign appointments to the MOC's 'spot'. And there are a few different ways that MOC's can provide their slate...principal or ranked competitive for example (refer to the tabs at the top of the nomination forum for more information...or scan the nomination section for current active discussion about nominations). This is very much a generalization, and also not publicly published.
The piece that OP was posting about, is when admissions has decided that they are the one to be appointed (assigned) for that MOC's spot at USAFA. Generally, usually, the SA notifies the MOC that 'candidate XX' has been offered an appointment from your slate. Usually, generally, the SA waits about a week to let the MOC notify that candidate in person, of the offer of an appointment, if they wish. Again, some MOC's do this, and some don't. After a certain period of time, the appointment is offered directly to the candidate from the SA. Usually via an email, to check your portal for updated info. And also via the portal. It seems to be hit or miss whether the offer is sent vias snail mail as well. Neither of my boys received the offer that way.
THEN, eventually, the "BFE" arrives. Usually quite a bit later. This is the folder, envelope, signed congrats letter that you probably have seen people posting their photo with.
If CAN happen, that a candidate is never notified from the MOC that they have received that MOC's nom. And then the MOC may not notify of the appointment offer...and BOOM the candidate receives an appointment offer. All due to timing. Not the norm, but it could happen.