Yeah I think it’s premature to say Yamato has CoC.
It won’t be a surprise if she does have it, but we’ve seen too many black lightning effects from non-CoC users like Ulti and Burgess for it to be certain yet.
One thing Oda’s has sometimes done to make it clear that CoC has been used is add a circular effect to the clashes
Which is absent here. It doesn’t mean that Yamato definitely didn’t use CoC, but you’d think Oda would want to make it absolutely clear.