If the fighter is practicing striking and resetting more rapidly? Yes. And 6 major mistakes (anything that takes time to recover from outside of resetting your stance) over the course of an hour is bloody low for intensive training. Which should have a lower rate than combat where you have to deal with the whole enemy moving and trying to foul up your actions, plus your whole system working at a higher rate. A 1-2% rate of mistakes like dropping your sword, having your blade turn in hand causing you to need to reset your grip, slipping do to poor weight placement/terrain and such actually seems about right for all but the most skilled and disciplined fighters.