Hmm. I wonder, then, where iaido fits in - all of the kata I've watched (and the one kata I've tried) in iaido start with a sword drawn from seiza...
I'm sure all those iai schools have their reasons for training drawing from seiza. Emphasis on training
, as opposed to actually representing an actual situation that occurred (as in samurai in seiza with their katana still in their obi). It's not all from seiza though. There are iai schools with a sizable standing iai curriculum. Also, schools like Katori Shinto ryu have iai but none from seiza afaik.