Australia did too. QR codes are probably the least invasive tracking you can imagine. You can open each one in a clean browser, like Firefox focus, if you like. They are just a shortcut for entering urls. If china wants to track its citizens, it’s not with QR codes as they track so much more from the data already on your phone.

Most places with public transport have moved from cash to card based payment. It’s all traceable already. Sure, some places, you don’t need to register the card and can cycle through some, but many places you need to register to use one, or register for reduced fares.