They do protect the port boats (or other give way boats) to a certain extent! If you don't use your right of way nice and early to block a guy a little, no fair jamming him out at the last second is sort of the point. I guess that's why they simplified the rules (!) to keep everybody focused on actually going around the racecourse, and if a normally right of way boat can't close the deal before the zone, just give a little room and keep going around. Of course getting everybody to act graciously is why rules are needed?
BTW, the UK-Halsey website has great little animated rules quizzes, with links to the relevant rules...