Here is the argument for the way it is currently, I personally don't care either way. What if someone has invested years in taking care of an account only to have the rules changed on you to solve a problem that doesn't really exist much in the older worlds?
You probably would not be happy. Also, as I mentioned, these changes are primarily designed to stop people from abusing multi's which is primarily an early server issue. Please don't misunderstand me, I'm not saying you can't abuse it in an older server I'm simply saying the issue the development team is responding to is primarily coming out of newer servers not older ones hence not making this a backwards change.
Anyway, we shall see where it goes, if people like it and if there is a clamor to turn it on for older worlds I'm sure they will consider it.