Still looking for some evidence to prove that.
I am more interested in why you think why Vergo's haki is far above Pica's. And for me, Pica being able to go full haki mode is feat that speaks for it self. Besides aren't you guys thinking that Vergo is god of haki just because he can go full body COA? Aside from being able to full body haki he was fairly confidante about Zoro not being able to cut through his haki even after witnessing Zoro's large scale attacks which hints that he has decent mastery over haki.