this is all accurate, but does not address the part about why its so important that it be anonymous.
The EU can still suck taxes from the transactions of Taler but at least they have no idea what you bought. Why should the payment middleman have a complete itemized dossier of your personal purchasing history just you and the merchant should share the details of the purchase beyond the total amount paid.
Because the government has a legitimate interest in taxing different goods at different rates.