Maybe Kizaru is a proficient swordsman and his confrontations with both Rayleigh and Shanks prove that using his named light-sword is the best option against a swordsman, better than his laser shots, which said swordsman could just dispel with either ranged slashes or, in Shanks' case, with CoC. I'd wait for the actual scenes to see how it was coreographed. Shanks doing a little swordplay while may or may not dominating and while maybe not even coating his attacks with his tremendous Haoshoku doesn't mean much.
Bro, the admirals spoke for themselves.
Aokiji (while turning pale): "Whoa whoa, are you serious?"
Kizaru: He hides a terrifying power
Doberman: We have to eliminate him now, or else he will turn into a terrifying enemy
Sure, it's not like Luffy's CoC outburst already dominated their will, but it they acknowledged that Haoshoku is too monstrous of a power. Stop denying that.