CoC was completely visible from Kaido and Linlin when the sky split
It is heavily implied (and Oda may have even confirmed, idk) that Shanks and WB used CoC
FURTHERMORE
When Luffy and Doffy clashed, it created a barrier and energy clash - their CoC is less developed, so obviously didnt split the sky - but CoC at a high level splits the sky when it clashes. It's a demarcation of power
Edit. As proof; CoC is illustrated through black lightning
Given Shanks and WB clashed before Haki was visibly illustrated to the reader, the absence of lightning makes sense but the general gist of the clash is the same