I always wondered how Roger could generate so much power with Kamusari. He sent Oden flying flying, not just pushed him back. Depending on the visuals it might be, that there's a two stage CoC infusion tech, similar to Zoro's Koh Three Sword Dragon. If Shanks is pulling out a tremendous amount of haki, I'm so on board with that assumption.
Might explain how Roger tackled Primebeard's Gura+CoC stack, basically just using a 2xCoC stack for such clashes