I thought this would be just a port starboard scenario. It isn't port's proper course to round the committee boat as per the drawing - right? If they both were on Starboard and overlapped, leeward couldn't use the boat as a pick and would have to give room but I can't see how this is any different than if they met in the middle of the line - no?

Hmmm...I'm going to have to read up. I guess blue would have plenty of gybe room in the middle of the line and the presence of the end of the line (the boat) changes that.