Paces are variable, and literally dependent on whatever a person feels like. Bella is also a short-stack on top of that. There are no actual static paces attributable to any person, and that was just a non-common measurement derived from an average. Which they applied to every possible step ever. When, again, they're variable and dependent on a person's mood. Everyone has control over their own gait.
Still subsonic.
It doesn't help that Meyer has been buffing her cast and otherwise well AFTER the book series is over and SB keeps bringing it in over and over again when they have mocked people for doing less than that.