Ok, either this isn't true, or the following is true:Actually it was confirmed after started g.l had fastest walk speed in game
GL might have the fastest speed once he gets up to speed, but he starts more slowly and has to accelerate to get there; which means that unless you plan to be walking loooong distances, Flash's walk speed is actually faster/more useful in footsies because he starts to walk at a higher speed right away with no floating/inertial/acceleration period.
If you are moving back and forth (which you are likely to be in footsies, or if you are walk/block/ducking through zoning) then the Flash would be faster in practice since he doesn't have inertia.
The Flash is one of the few characters in the game that can play SF-style footsies, which is pretty cool for him.