We never know, and there has never been even a hint of intrigue about someone like our PD actually knowing earlier than the rest of us.
The only two things I can think of is that you told another program you were ranking them first, and word got around. Or perhaps you didn't match (post doesn't have that desperate feeling). Programs, I think, get to see who didn't match that applied to their programs.
And I think I remember - not certain about this - that programs get a list of where all of their applicants matched, and maybe that list comes out on Tue. IF true, then they actually get a de facto match list on Tue. bec. they can just figure out where everyone on their app list went. Seems a little stupid that I would be breaking this news to the world, so I'm not very confident it's true, but it would explain why you got the survey.