@runningaway123 - it is confusing! As I understand it, although they may have met their enrollment goal, if any of their students who accepted a spot at American wind up getting an offer from their first choice where they may have been waitlisted and they decide to take it, a spot then becomes available and anyone still on the American waitlist may get a call to see if they’d like to accept that place.
However, I think the further into May you get, the less likely that is to happen, but you never know! A friend of mine last year told me that her son finally got a call from the school that was his number one choice at the beginning of June, so it can happen. And he said yes - which of course started that cycle of a spot at the school where he’d already committed becoming available, and then someone else getting a call from the waitlist to see if they wanted to go!