It sounds like it's making more sense as you chew on it. There is where "competitive play" becomes an issue when role playing. You can't force anything on anyone else in role play, and when you try to, people end up resorting to silly measures in order to "not lose" like metagaming or godmodding.
For those of us who role play, we enjoy the story - good and bad and we understand that unless you want a flat, uneventful story where nothing happens, you have let others succeed sometimes. Bad guys needs to let the good guys have their moments of victory, good guys needs to allow the bad guys to cause trouble and harm. When people get all attached to their characters and decide to be invincible or all powerful, you end up with these boring games where nobody wants to do anything for fear of looking bad. In this context, the player/character separation rule makes a lot of sense.
We have had many long running BF story lines that were possible only because of this sort of mutual cooperation. Generally, when you give someone a little space, they end up giving you a little space in return at some point. ( at least, they should ) It's a sort of unwritten rule or courtesy that good players will typically honor.