On this video it is noted that Harrison was increasing power as he was repeating what he thought were the controller’s instructions. If that is what happened, that apparently eliminated any chance for the controller to hear a bad readback. Just short of the holding line, I wouldn’t move an inch until I’ve given the controller a chance to catch a bad readback - wouldn’t take but a couple of seconds.
https://www.youtube.com/watch?v=nU0BmAWtz5c&feature=youtu.be&fbclid=IwAR1urNgcg2fIBYrla-OqaHOzE1nSLxMHO2nYz6ekO2hfjZebcUvhIaRWJOs