Va is not the same as Turbulence Penetration. V turb is based on a certain velocity gust impinging on the aircraft (25 fps? 50 fps? Instantaneous? Over a defined period? Can't remember the details.) One is about externally caused forces & accelerations, the other about what the aircraft can do to itself.
Provided no limits are exceeded then it's entirely possible for a manufacturer to specify a single speed for both conditions.