Personally I see the Kb swing ( which must be with a heavy kb) helps mostly with the eccentric / isometric contraction conditioning which in turns aids system stiffness. Not necessarily the speed at which a muscle contracts but more the quality of its contraction against a negative force.
We have to remember that “slow twitch” muscles still contract approx 14 times a second, and I’m pretty sure we don’t take 14 steps a second. It’s how we’re training the force being generated to be handled.
I find it hard sometimes to load the body eccentrically with enough force under tension. Yes, we have the squat etc but in reality who is really resisting the force ( no Star Wars comments! ) at the bottom in the same way you have to with a swing.
Just my 2p (2cents)