This may be a silly question, but considering that it is not illogical to assume that it was known from the beginning that the virus posed no real threat and that the mortality was irrelevant, I wonder why China found it necessary to control the situation. What exactly did they want to control? Were they trying to control the infection with a virus that might have simply passed as a bad flu season?
I'd say that protocol required that they assume the worst. As soon as they looked at it and determined it was man-made, they activated their bio weapons protocols, or some version of them. They weren't about to sit around and wait to find out if this man-made virus (likely from the US) was really bad ju-ju or not. They could figure that out as they went along. First order of business was to protect the population. Notice that as soon as they were sure that it wasn't much of an issue, China pretty much dropped the whole pandemic thing, leading Western leaders to accuse them of "under-reporting their cases and deaths".