The number of confirmed COVID deaths in the US is almost a million, so "millions" doesn't seem that much of a stretch for a much larger country like China. Of course this is not directly comparable because the number of deaths depends on vaccination status and age demographics.

And other countries with fewer deaths have higher vaccination rates. China has the problem of both, low vaccination rates in the risk populations and worse vaccines than the mRNA ones.

But lockdowns can't work forever, I don't see how this is sustainable without dramatically increasing vaccination rates and getting better vaccines. Lockdowns only gain you time, you still have to do something useful with that time.