It is common knowledge that for those who have grasped the true essence of the sword, the physical shell does not matter, as they can make a random stick a divine weapon, or a fleeting gust of air into a work of divine craftsmanship. Such is how 自分's skill level can be described literally, not metaphorically, poetically, or rhetorically, but literally how skilled 自分 is w/ Swordsmanship itself.