You've already mentioned that China has been adding to its pocket a number of countries by loans as part of the belt and road initiative. Afghanistan is just another link. Their success will depend on how they deal with the Taliban and other warlords/remnants of the Northern Alliance. If China is willing to just pay money for access, I doubt they need to actually bring in forces if they are willing to deal with everyone and accept some loss due to some inefficiencies, i.e. bribes.I'm suggesting that what is new, is China's aggressive territorial policies, and the extent to which they will go to secure an increasing supply of resources from outside China. They are making many incursions along their borders.
That said, as both you and Sags have indicated, this is not new - and it likely won't end well for China or any other country/army who tries.