I understand the point. I still maintain any totalitarian communist regime is going to spread absurd propaganda in such a situation pretty much no matter what.
The lab escape theory is certainly completely plausible. But it becomes no more or less plausible just because there's "US military conspiracy" propaganda spread by the government.
They easily could've done that to counter all of the accusations hurled at them by US citizens that it's an intentional bioweapon, or due to Trump calling it "the Chinese virus" and constantly trying to associate it with them, or to pull attention away from themselves due to the outbreak starting there and just generally to reduce embarrassment and spread confusion that they hope will improve their reputation, or even specifically because of posts like yours.
If you assume for the sake of argument that the lab hypothetically isn't responsible, but lots of people think it is, this would be one way to provide such a distraction. It would as well if the lab were in fact responsible, but that definitely doesn't mean that's proof the lab is responsible. They have a ton of possible reasons for why they would want to spread this propaganda.
The hypothesis that "they're more likely to spread propaganda about the US military causing it if their lab caused it" carries a ton of implicit assumptions which may or may not be true. It's reasonable to speculate about and discuss, but it alone is evidence of nothing. If there were some leaked document saying something like "hey, since our lab fucked up let's distract people by accusing the US", then it'd be a different story.
Of course, China's government promoting and spreading absurd conspiracy theories needs to be condemned no matter what, but an analysis of the true root cause of the outbreak needs to be totally impartial and objective.