For me, the randomization of the DHS ToT has realy hurt the ride experience. I would say that 3 out of 4 times, there is almost NO thrill factor anymore. When you do get the complete drop version, it is awesome!!!
Someone else will have a comprehensive answer, but I DO recall that the two rides are actually built quite differently. The FL ToT has a load zone and then the elevators move forward through show rooms into the shafts. At DCA, the elevators do the drops in the same shaft as they load.
Umm, here is a link to the FL tower of terror blueprint. FL ToT I can't find one for DCA but, at DCA the loading and drop are in the same shaft. So maybe it can't be randomized for safety reasons?
Or it's just laziness. The DCA ToT was built on a much smaller budget.
No, when you load your elevator moves backwards into the drop shaft. They do this so one can be riding in the shaft while one is loading, that's why there is two loading floors. When you get in the elevator look strait up, there is a ceiling. You have to move backwards and into the drop shaft before continuing upwards.