Thanks for the interesting article! The testing might have to do with fear of mutation in 2nd and 3rd wave infections from other countries back into China. The article below is about cross-species transmission. Yes, COVID-19 most likely live in different types of meat.
https://onlinelibrary.wiley.com/doi/full/10.1002/jmv.25682
There is also a theory about the earlier virus carried back by American soldiers during their training in Wuhan before the outbreak to be even more virulent (aggressive) than existing ones in China. Viruses are complicated as they mutate at different rates within different organisms and different environment. When they mutate, researchers need to readjust vaccine formulation and target region to induce immunity.
Here is the article about the L strain (aggressive) and S strain (less aggressive) within China itself.
https://www.livescience.com/coronavirus-mutations.html
https://academic.oup.com/nsr/article/7/6/1012/5775463