How? Are you suggesting that people will now show criminal evidence online just to prove that they got a cease and desist? That would be beyond stupid, and I don’t think there’s anything in the article that suggests it. There are other ways to prove it, such as asking Flock’s legal team (if they say they did, it’s because they did), or verifying if the letter has a consistent format and return address with other cease and desist letters that the legal team sent.