In Musashi's era, meaning the late 1500s, kendo (sword fighting) was absolutely about being as "productive" (read: lethal) as possible.

As it happens, this was also the era when firearms had just been introduced to Japan. In 1575 Oda Nobunaga demolished the Takeda cavalry at the Battle of Nagashino, marking the first time firearms had been used at scale in Japanese combat, and in 1600 Musashi participated in the decisive Battle of Sekigahara where both sides used them extensively.