Is it possible to dispose of bodies by the million without the world noticing somehow?
It's not so much the 'disposing bodies' as much as 'removing from normal life' that is the issue. For example:

Chinese Tycoon Who Criticized Xi’s Response to Coronavirus Has Vanished (Published 2020)
Ren Zhiqiang appears to be the latest government critic silenced by the Communist Party as it cracks down on dissent over the epidemic.
Now, we only hear about this individual because he is pretty influential so news worthy. But people notice when a friend disappears, and will spread the news. If 21 million (?) people disappear this news spreads like wildfire.
Something to consider: if you think 'communist ' China has the same level social security net as we have in Western Europe, think again. I am pretty sure Chinese-style lockdowns financially ruined endless numbers of Chinese citizens, and CCP is not the kind of government that cares much about such 'details' when it acts.
I anticipate a fair number will be kicked of their subscriptions in the US in total as well, three months from now. My estimate is half the effect (0.5*1.3%=+-2 million accounts) due to US relative wealth compared with China.