Conspiracy theories have since been his only hobby beside bodybuilding and preaching on his yacht.
Such an assertion is well within the bounds for what should be considered possible. China's style of governance lends itself very well to extinguishing epidemics (namely, they can take swift and decisive action), so it's not a stretch to imagine that they would be affected by the outcome less than the USA in the longer term.
If that is true, your source doesn't show it. It says that a media outlet owned by Guo reported that "the Chinese government prepared to admit that the virus came from a lab".
Not that it was engineered, not that it was intentionally released and certainly not as biologicial warfare to defeat the US (somehow by releasing it inside China).
https://www.buzzfeednews.com/article/janelytvynenko/a-site-t...
It's hard to doubt Miles Guo's credibility: it is as solid a zero as they come.
To be fair, it's not like he's the only one who spends money to publish lies to brainwash people. Nearly every political party and government does that, although only select few would lie to such an extreme degree.