This happens many times a day on Betfair, the shorter the odds the more money it attracts that's why betting the home "certainties" in the EPL returns a profit long term, the bookies are only looking to balance the books not tell you what they're probability of particular outcome is, perhaps they shortened their odds to attract the big wedges so their exposure wasn't so dire in the event of a YES vote, who knows, it certainly wasn't done because of anything that was happening in the independence debate as far as I can see.