Look at the link - does it have a token on it to identify that particular survey invitation as the one they sent you? I’d wager that’s what happened rather than it being some deeper tracking. A stock standard survey monkey survey can do the same thing.

108 days of the year fall in that end-of-the-month window where they belong to the astrological sign associated with the month that follows, so almost 30% of all possible birth dates become harder to guess. (Your comment made me curious as to just how significant this variability could be in practice - a lot more than I would have guessed)

That would be a bad idea if the “correct” option is available. This is a DoB check without actually displaying your real DoB on the page, which could be used as PII verification by a malicious actor. If the correct astrological sign is listed and you say “Does not Apply”, it will count as a wrong answer.

Crappy way to do this, but they’re trying to walk a line between confirming your identity (or at least that you know the sensitive data of the person you’re spoofing) with multiple choice questions and not creating a security vulnerability where someone can leverage their site to compile sensitive data on individuals.