Use Google maps to see how big the surface area of Wuhan is, I have no idea how they could even think about keeping people from leaving. "Wuhan, the vast capital of Hubei Province, in central China" 8,494.41 km2 (3,279.71 sq mi) 11 million people and the Yangtse runs through the middle. Its Tet in China everyone goes home for the lunar new year starting last Wednesday, its what they do.
China has been known to under report many things like levels of air pollution no reason to think they didn't keep the wraps on this for a while
