[Survey8430]

The way I see it:

If the participant has to trust the survey creator, then it is not anonymous. The survey creator can link the data.

If the survey creator has to trust the participant, the survey is anonymous. The participant can lie in the survey, lie about participating, or submit the survey multiple times.

Your example was not anonymous. But you did not break the participant's trust, thank you! (Or maybe you are lying.)

Anonymous example: Sending a clean link to people to take the survey. If not enough answers have been received, a reminder can be sent to all, with a clause, that says: "if you have already done it, you can ignore the reminder."