This about anonymity applies for whistleblowers which the forwarded article was about.

Not sure I would rely on that, but Xerox's docs state that the requirement was introduced as an anti-counterfeit measure by some governments. Counterfeiting currency probably wouldn't be a concern with B&W printers.

Most banknotes are not printed on ordinary paper, but it doesn't stop people from trying. Printers which produce those dots will also usually refuse to print high-resolution pictures of dollar bills.