And just for domestic propaganda reasons. If it came from China they could be blamed for it, and they want to deny/deny/deny and defect blame. Serves their propaganda purposes to have people believe it was imported and generates an us-vs-them bunker narrative where the rest of the world is unfairly blaming them. That leaves their citizens questioning the rest of the world and not their own government.
https://www.npr.org/sections/goatsandsoda/2020/06/28/8839000...
https://www.nytimes.com/2020/06/07/world/asia/china-coronavi...
etc.