I would guess that it might be something to do with the diameter of the turbo. I believe the LC turbo is smaller than on the LCR. Probably similar to when you have a smaller fan on a computer. Because they have to run faster to get the same air flow than a larger fan they make a lot more noise. I suspect a smaller turbo will be flowing air quicker than a larger turbo ( that doesn't mean it's flowing more air however) and this may lead to a louder whistling sound.
I could be completely wrong though.
cuprablue