I can't say for the privacy policy, but I used Clue for over a year without an account. Since I forgot to do a final export of the data before resetting my phone (I know, I know...), I subsequently lost all the locally stored data for the past few months. When I contacted Clue, they said their was no way to retrieve it. So my guess is that they are telling the truth re: nothing sent to the cloud unless you explicitly choose to.