Only one had 3 but you could cheese the second one if you were clever with the environment
Genichiro and Demon also had 3.
Posture is just another health gauge that refills super quickly, meaning even a slight screw-up undoes any and all progress you made. In my opinion it really isn't any better and in some ways it's outright worse.
It rewards skillful play, if you are good you can defeat the bosses much faster, while still having the other way of depleting their health first if you want to take your time to learn them (what I did in my first run).