Here is what the SIs said. The blue flag was up all day.

I have been looking at them and the rule book and can find nothing to say either way.

9. START / FINISH LINE OBSTRUCTION
9.1 START LINE OBSTRUCTION: The Start Line shall rank as an obstruction for fleets previously started while other fleets are starting and in sequence until after the last fleet has successfully started.

9.2 FINISH LINE OBSTRUCTION: The Finish Line shall rank as an obstruction when a Blue flag or shape is displayed on the Race Committee boat at the finish line for boats not finishing.