The government (and party) only acting in their self interest means they'd share and push any explanation that wasn't nefarious. No they don't have to do anything, but an innocent explanation is something they'd benefit from by disclosing.
You're applying the logic of a democracy with a free press, which assumes people will talk about it. You also probably think that China worries about what you think and that they would care to address your concerns, when the 1.4 Billion Chinese citizens is of much greater concerns to them.
This is the same delusion that Western intelligence agencies like the CIA had with Saddam Hussein. Everyone expected that his putting up a fight against the weapons inspectors was a very clear sign that he had something to hide. If he had nothing to hide why not let them in. After the fact we found out he didn't actually have a functioning weapons program. His failure to be open to the weapons inspectors seems deeply weird and irrational from the perspective of a Western Democracy. But he was running a strong-arm totalitarian state. He needed to stand up to the US and the rest of the world for domestic political points.
China doesn't care what you think or what the US thinks. China cares what 1.4 billion Chinese think. China can better control what they think by flat-out suppression of information, because they've built those systems of control.