Must be because Oda plans to have Zoro "master COO" mid battle in order to beat Shiryuu. Seriously this fruit is borderline useless against top tiers since most of them have good COO.
I cannot fathom why Shiryuu gets this fruit over tons of much more useful fruits for pure combat. Sure its nice for sneak attacks against guys who don't have high level COO but thats it.
So far Zoro has good COA, just started using COC but he lacks COO feats. Most likely his COO is still on the weak side so this makes sense to me.
And oda has shown that he has no problem with guys upgrading haki mid battle.
I cannot fathom why Shiryuu gets this fruit over tons of much more useful fruits for pure combat. Sure its nice for sneak attacks against guys who don't have high level COO but thats it.
So far Zoro has good COA, just started using COC but he lacks COO feats. Most likely his COO is still on the weak side so this makes sense to me.
And oda has shown that he has no problem with guys upgrading haki mid battle.