Because of the cut out in the door for the wheel well, there isn't enough room for the glass to go all the way down. Just be thankfull it goes down that far. Without the quarter glass in the door,if that whole window was one piece, it would really limit the amount of travel the glass would have, if any. Guys, that is the reason that quarter glass is there.
Will

 

This is what I understood too but this does not explain Jon's Aristo. The body should be the same so I am not understanding how his is going all the way down (OEM behavior).

 

Maybe US GSs have thicker side impact door beam? which limited the window going all the way down?
It can't be a safety issue, since I can fully lower the rear window on a LS.

My old Volvo 850's rear window only goes halfway down

 

Jon probably has some kind of telescoping window glass he had made by NASA

 

Better than my '99 Tahoe...because of it's ingenious designers, my rear window only went down like 6 inches!

 

yeah that's what i am wondering too. if ti's a physical limit then i can't understand why jon can do it. that's why i demand pics

plus, if it works in japan, then i don't see why toyota has to make another module to lower it just that much for the US version