Hi Nathan,
I believe (personal opinion alert!) that the reason for the explanation of attack in iaido kata is different than what alot of people now tend to think. It is important when performing solo kata to be able to visualize an opponent to strike at. I can stand and watch and tell when people are not doing that, it changes the entire range of motion. My belief is that the explanation of attacks (bunkei ?) was originally to give focus to the kata, not to simulate an actual situation. I do agree that I have heard people describe a patently impossible situation as the reason for the kata. There it is, my thinking on it for what it's worth.
Cheers,
Paul Smith
"Always keep the sharp side and the pointy end between you and your opponent"