As a result of the ban, many miners do not keep bitcoins in their mines, which has already led to the collapse of bitcoin mining companies.
BTC isn't kept or stored in "mines", BTC is stored in BTC wallets. BTC mining companies also didn't collapse, some of them just relocated out of china because of their hostility to mining, and we cannot also be sure that there aren't some mining companies still mining BTC underground in China and using VPN to hide their IP addresses.
Now as far as I know there are no miners or mining companies in China.
We cannot be 100% sure that mining hashrate in China is now at 0, surely it has gone down, but there are probably secret miners still mining BTC in China.