That is correct. I have seen people put them in facing the window for better dispersion but you loose some of the imaging and RTA more often than not. You can hold the tweeter in a few places to see what it will sound like, who knows you may like it like that.
my tweeter is placed on the dash board facing the top most part of the winshield, while my midrange is placed on the door, facing thte ankle of my foot...do you think i should change their posiition ?