I don't doubt for a moment that there were plenty of practical reasons for being able to attack on the draw, especially when the form of the weapon makes it relatively easier to do so. I just suspect there's a little more to it than practicality alone simply because so many JSA practitioners make such a show out of drawing and sheathing the blade with dramatic deliberation. I don't know of any other culture that made a whole art with its own name out of drawing the sword and putting it back, even though they all faced murder on the highways and nighttime assaults and all the other types of violence that man can conceive. The reason for that is clearly cultural, and I don't think the samurai looking macho and intimidating drawing his katana is any sillier than the Spaniard posing dramatically before killing the bull or circling you with rapier poised on high like a scorpion's tail, just another form of psychological warfare. I think Mr. Tallebois' point about the effect of cultural norms, taboos and protocols about allowed usage of weapons probably plays a large part in this difference of style. I didn't mean to sound condescending, just a wink and a nod to a warrior's display of pride.
I'll just put things into perspective here. Many styles have a part of their curriculum that they call iaijutsu or battojutsu. It was a specialised skill but not intended to be a stand alone art. There are only a handful of schools that concentrate mostly on drawing. Why? Well as was the case in the west, students came for diverse reasons, they were not expected to stay their whole lifetime in the school and they may have joined a couple of them if they could. They were also expected to have been taught swordsmanship prior to it by their father or clan instructor. So I suppose that one would have a solid base of swordsmanship before joining a iaijutsu school to perfect those types of techniques, or being in need of a fast self defense option because he suddenly didn't felt safe anymore, or being sent by his Daimyo to dispatch a noisy shogunal agent. The fact remains that it would not have been as widespread and popular as it is today, for some reason (personally I find watching a class of modern iaido as interesting as watching paint dry, but to each their own). And many styles practiced today were invented or separated from their kenjutsu counterpart in the modern era.
That said, if Thibault was worried about being caught in the act of drawing the sword and offered advice to avoid it, then surely the Japanese must have had similar concerns and methods to deal with it unless there were cultural taboos against things like tackling a guy before his weapon is drawn.
That is precisely why the resheathing looks so dramatic (although I think a big part of it is due to modern concerns). If you're looking down at your sheat to get your sword back in, thinking all is safe, an attacker might come out and dispatch you while you are not aware. As for being attacked while drawing, there are techniques where you step back while prior to or while cutting or stabbing, but I think the idea is to cut faster than the other guy can touch you. Concerning the cultural aspect, there are no indigenous art I know of that don't include esthetic aspects from their culture, be it a way of stepping, standing or some other decorum, even modern ones are by their adherence to strict practicality in form and function. It's all part of the fun I think and gives them their unique flavor.
The plate in Talhoffer which you can find in the "Fight Earnestly" file in the Historical Manuals section under Talhoffer, seems to be followed with a plate showing a descending false edge blow that seems to be striking across the body's stance from left to right to end the fight, which may indicate that the fight went on for a blow or two between the draw and the end.
That's a common occurrence in iai. You are not necessarily expected to kill with the one handed draw, so a second cut is often needed.


