The reason for that is the 119.1 frequency was stopped as the tower frequency that night. They switched to 123.9.
As a pilot is seems a little suspicious to me that the controller issues the command "..runway 22 right taxi position actually I have a message for you to go back to the gate immediately...", all stated in one breath without hesitation. Normally in air traffic control and ground control communication protocol there would never be a last second interruption in the issuance of a command such as this because, the information needed to "taxi into position and hold" which is what the tower controller was about to say, would have already been "made up" in her mind and she spoke as though someone, last minute, shoved a piece of paper in front of her or that she received some emergency print out over-riding her command. It just does not happen that way. And if someone had "flagged her down" there would have been some type of hesitation in her voice, or at the very least, she would have said, "Emerates standby". I'm presuming the "authorities" intentionally allowed this part of the case to unfold with this drama so as to create the impression that he narrowly escaped and through that drama, change the law regarding notification to airlines, and give some boost to the pressure from the Administration to switch notifications from the Secure Flight program to the TSA.
As much as you say ATC just doesn't work that way, law enforcement doesn't work that way. They aren't going to narrowly let a plane take off with a suspect in a terror threat just to dramatize the incident. Heck, if the plane had just pushed from the gate, the news would be reporting it as "SUSPECT NARROWLY ESCAPES" as some outlets may be doing now. They don't know the difference, nor do they care. The news is the one to push the dramatization, not law enforcement.
Not trying to be rude but that is just ridiculous. It could just be that the Tower Sup or whoever got the call and came over to tell the controller.
Regarding the "no-fly list," some radio news outlet near me is reporting that the policy was for the airlines to update their list every 24 hours, which would mean when he was added, the airline checked an outdated list. That policy has since been changed to 2 hours. However, I cannot promise how accurate that is.