I mean they did fought for an extended period of time off panel right? And nothing showed that Marco struggled to keep up with Kizaru's speed and assuming Kizaru didn't use his speed at all during Marineford is a pretty big reach IMO.
And yes, Rayleigh was also able to keep up with that speed. I don't disagree with that.
And yes, Rayleigh was also able to keep up with that speed. I don't disagree with that.