Firstly, I haven't misunderstood anything. I have copied and pasted EXACTLY what it says in the rule book. You want a fight about it, take it up with the USGA and/or R&A or, as apparently people are reluctant to do, accept that you are flaunting the prescribed behaviour as given to you by the governing bodies of the game you love. We can all disagree with all sorts of bits and pieces in the rule book. That doesn't mean we disregard them.
If it's still confusing to anyone, let's break it down a little more: if there's some space in front of you and the group behind catches you up, have the manners to get out of their way. As Jon W so rightly pointed out, it shouldn't need to be written down for you. Clearly, contrary to what John K has written, the moment the faster group has gone through, you are free to play, given that space will not have already developed and you will not therefore be required to move again, although obviously you will before long if you are slower than the next group.
As I understand it, Jon W and I both grew up playing the game in a certain way at a certain type of golf course in a certain country. And I can tell anyone from further shores that the same system we grew up playing under is the one which has been proven, time and time again, to allow groups to comfortably, without rushing, play 18 holes in 3 hours. It's a system which John K laughably infers is in some way a new stain on the game. Reality is that it's a system which goes back to the early days of golf when it was bloody obvious to anyone with a brain that you simply didn't deter other chaps from getting on with their own games. Of course, the game has long been plagued by the righteous self-centred; those whose insular perceptions of the world have flatly prevented them from recognising just how ill mannered their actions actually are. Nonetheless, a procession of ignorance doesn't, by default, dictate an acceptable or workable pattern of behaviour.
Think of a motorway. Does it work better when people decide to park in the middle lane at 60mph or when they are obliged to follow the correct overtaking policy?