Kumitachi is a drill... and has much less to do with "real" than "real".
This again, depends on how you train. If all you do is follow the movements then all you are really doing is dancing with a sword.
However when sensei really tries to hit me, i better have studied the kata and learned to move correctly or risk getting clocked on the head. (never has happened in our dojo of course as sensei is very skilled at stopping inches from our face)
In sword, if you move too early, your opponent tracks you and kills you. If you move too late, he kills you because you were too slow. The kumitachi again serves as a way of training yourself to move at the correct time. And when we work with sensei, he knows when we do and when we don't.