Which quiz are you talking about - #16? I'm not sure what your question is, but I think the point of the example was that you can't just call "no room" to the windward boat. You have to close the space, otherwise it is freely given. In the example, the leeward boat waited too long to close the space. They turned up when the windward boat had no place to go and caused the collision. If you are going to enforce the leeward rights, you actually have to do it (far enough in advance), not just make noise.
I think the other point is that if you are attempting to reach into position, you are asking for trouble. In JD's video, he was close hauled tight against the committee boat. He didn't have to turn up (or at least it was imperceptible in the video). The reaching boats found out they had no room before they got to the committee boat. JD gave them a warning in advance that he wasn't giving them room … that was enough because he already had them closed out.
Contrast that to your opening remarks about a boat that chronically "barges" into position. He's doing it because nobody is closing him out. You can't just complain, you actually have to take the position away from him, otherwise it is space freely given.