I will concede that I probably mixed heading up and mark rounding together to arrive at rounding up.

I am interpreting this picture as the end of the run for them. They are sailing deep and dousing the spinnaker. If we were to back up everyone 3 boat lengths to when RUS entered the 2bl zone there was only one boat ahead of a line drawn along its transom. It was the gybe to transition to upwind that brought NOR in front of this line.