True, but only if you monitor Bobs purchases. Funds are anonymous until you see them leave network. And that might be years or decades in the future. And one sale/purchae on uncontrolled exchange breaks the chain.

The chain is unbroken. If at any point you identify the owner of a wallet, you then find out the full transaction history of that person. That is the problem with putting all of the data in an append-only ledger that is pseudonymous.