This sounds like it won't do a thing to most people. To me it makes sense (honestly). When you call LGA the first thing they do is give you a code, give you a Class B clearance and climb you to 1,500' and shoot you straight up the river. No crazy manuvering required.
For someone used to operating in that area I agree it can be done safely (there is a banner tower guy on here I believe who does it) but something like this will prevent the majority of weekend warriors from trying to do a pretty tough turn.
It sounds like a knee-jerk reaction (and may be in part) but if they keep to what they have done in the past it actually has a little rhyme and reason to it.