Bitcoin is quite different from cash. It is traceable. So the authority will know the flow of bitcoin transaction.
the movements are traceable not the owner, cash is also traceable if you take it from atm, so unless you counterfeit it i can't see how cash is not traceable nowadays
If you buy something with cash from an ATM the change you get is untraceable. If you wanted to launder money from an ATM you could buy a small value thing with each bill separately until you had none of your original bills remaining. The change in smaller value blls would be untraceable.