Very good theory! That does make some sense.
I think also though there is another factor involved that has been addressed by some of the guys doing the mod. I think the BMW engineers got a little bit sloppy on the design of the valve cover baffle and in the way the vent tube comes off the valve cover thinking that the oil seperator would take care of any oil that got sucked in to the CCVC. By doing the mod (depending on how you go about it) there is less chance of the little bit of oil that collects on the bottom of the valve cover tube to getting sucked out.