^ sorry thats not true.
It totally depends on the speaker, the angleing of the speakers and the car.
If you have the tweeters and the mids apart, eg the mids in the doors and the tweeters on the dash or in the a pillars, you will drag the stage hieght up, but youl get cronif seperation, (your brain is told where the sound is coiming from by the high freq) this can be helped with very high xover points but not always.
It is best if the tweeter and the mid are close together, and there voice coils are on the same axis (forgoten the proper name for it) so in this case as the tweeteres are mounted ontop of the mid, the voice coils are perfectly allinged.
Although on a down note if you were to mount the tweeter in the door as standard and not in a door or kickpod (or just angled in the door) then your stage will be very low.