When my DS went to MMI, they did not find out all at once, USMA left the communication to each cadets' own MOC. He got his notice in mid Jan (a few years back) and others did not find out for many weeks later (this was back when rolling admissions was the process) and it seemed like there were 3 or 4 "waves" of appointments being offered. His BFE was mailed to his home address, we had to ship it to him at MMI, but emailed him a photo we took of the unopened package (did not want to take away the pleasure of him opening it himself and being the first one to see/touch it).
So if things have not changed that much, it would not surprise me if there was not a uniform announcement to everyone at MMI, that being said since USMA is no longer doing rolling admissions, I could easily speculate that a bulk of the notifications might be at the same time so it might seem as if they were coordinated and I would still expect that USMA would at least offer the MOC to make the direct communication.
Just my hunch.