[quote=@Unoedipal]
<Snipped quote by IncredibleBee>

Because it's the crystallization of his legend as someone who used improvised weapons, and we have an A++ Noble Phantasm in canon that does something of an incredibly comparable nature.

NPs aren't just magic items, they're crystallizations of feat.
[/quote]

Yeah, but Musashi's is also much more situational. He can only use swords and sword-like items, like bokken and baseball bats.