“...This is a big deal because it took a lot of people all screwing up in their jobs for this to happen...”
Exactly. There could have been no “mistake” here. As you say, FAR too many people know which planes are certified, especially the pilots, amongst many others. They should be fined heavily for that.
This type was just recently certified, and since all AA A321s are overwater, and all are identical except paperwork, it is possible it was a mistake. A bad one, but not hard to see it happen.