Hell Haki explaination has been long before the timeskip needed, imagine Shanks used CoC supposedly since the beginning, Shanks vs WB splitting the sky, CP9 all of them supposedly having BOTH CoO and CoA, Zoro using CoA in Alabasta, Skypiea with CoO
500 chapters for a vague explanation, another 500 for little tidbits of it even tho it should be even more common than df's.