One thing does strike me as strange. The common ancestor here, RaTG13, was only sequenced and published by Shi's lab in Wuhan in late January. Despite supposedly being sequenced in 2013. Shi's Wuhan lab is the same one in question in this article regarding a potential leak.
Is this unusual for a lab to do, or is this common practice?
Others have asked this question in the Twitter thread you posted, but no one has responded so far as I can see. E.g:
https://twitter.com/LizSpecht/status/1223394697948753922 and https://twitter.com/LizSpecht/status/1223451393173803014