Tony
I believe that the provision regarding space for a dribbler to get between defender and boundary is precisely why this rule makes sense - if that rule is enforced correctly. I think that coaches learned to teach players to go all the way to the sideline because refs generally go with the dribbler when the dribbler tries to get around a defender at the sideline, even when there is not sufficient space. If defenders stop short, offensive players hit them "off-center," rather than in the middle of the torso, causing a collision that many refs (in my experience) interpret to be a block. I am not saying this because I think calls went against me - I say this because I see it consistently called this way for all teams.
If the block/charge call is consistently made correctly in these "no room to get by" cases, defenders won't need to go all the way on/over the sideline to cut off the dribbler. As for a CYA, call it what you want. They admit that they didn't make it clear enough in the rule book (they will fix the rules next year), but they are also stating that this clarification lays out the specific intent of their rule change this year. When I initially read the change, the clarified version is what I thought I read anyway, as did many others. So for some it is a clarification, for others a confirmation
NF can't fix the book until next year. They say they will do this. For now, they can try ensure that people call it the way they intended it to be called this year by clarifiying the meaning of their rule change.