If the email/survey was not simply sent to people who had not already filled it out, then
I know I'm going to get trashed for saying this, but maybe whether or not you received that email actually does reflect something about your match status. It just seems very strange that some people received it and some didn't. The only explanations I can think of are:
1. The email/survey was sent to people who didn't match, to see why they didn't match to help provide advice for future applicants.
2. The email/survey was sent to people who matched to see what they did to increase their chances of matching.
3. The email/survey was simply sent to some random people to get a random population of applicants to answer the survey questions, or test the email service.
It also seem suspicious that it happens exactly a week from when we will actually find out.
Regardless, it is not cool to send an email like this before match results are out.