[tripletao]

That's correct but out of date. RaTG13 used to be the closest known bat virus to SARS-CoV-2, but (a) it's far enough that there's no simple path to derive SARS-CoV-2 from it in the lab, and (b) it's not anymore, with the discovery of BANAL-20. The WIV was also sampling in Laos near where BANAL-20 were found, but hasn't published any closer genomes.

For the conspiracy-minded, I'd note that the WIV had published a subset of RaTG13's genome pre-pandemic, enough for others to identify the similarity. So they pretty much had to publish the rest of the genome post-pandemic, since it was obvious they had something interesting. The WIV used to have a public database of viral genomes, but it went offline around Sep 2019. They cite "hacking attempts" as the reason, but still haven't reinstated it in any form.

I'd personally guess that the Chinese government doesn't know whether SARS-CoV-2 arose naturally or unnaturally, and doesn't want to know--their preferred story (imported into China on frozen food) is near-certainly false, so no truth can benefit them. It's very hard to say though, all pretty mysterious. There are significant unexplored paths for investigation within reach of American subpoena though, e.g. in any cloud services used by the WIV for genomic data.