I don't see how this is surprising at all. If you were given 20 days to vote and people voted randomly then you would expect about 95% of voters to have voted before today. Given that voting is an important thing that you probably don't want to procrastinate, I expect more than 95% of people would have already voted. On the contrary it is probably habitual to wait til the big day, but I wouldn't read too much into that number.