It seems you have never even listened to both to conclude such. Despite being planar and dynamic , the point here is that they sound SIMILAR that's why alot of people have been going back to HD650 from LCD2
I owned the LCD-2F for about a year, after spending a lot of time in shops and at meetups with the 600 series (and even briefly owning the 660S.) I guess I just disagree with your conclusions. They are very different to my ears.