This may or may not be true, but its the same sort of reasoning that was used to justify the Iraq War and we all know how that turned out.

Before the war, Saddam was acting unquestionable suspect by not allowing inspectors free access to locations and constantly moving material and persons around. In truth, it was a presence. A chemical weapons program was expensive, and hard to keep safely hidden so Saddam simply pretended that it existed by acting like he had something to hide.

As for China, it could be something as simple as regional managers hiding poor response times and safety violations that would have their heads rolling. It doesn't mean that there was a leak intentionally or unintentionally.

Disclaimer: I'm playing the devil's advocate here. Having a corona virus outbreak in the same city as your military installation studying corona virus is suspect.