Coles notes version (and only my opinion): day traders are playing a straddle, meaning opening both puts and calls on the stock at the same time; not only that, changing their position within the straddle every 5 minutes. A straddle is another hedge strategy to extract fractions of a percentage of value while protecting ones position with bets in the other direction.
So...he's thinking there really are not too many seriously long term "short" positions on the stock because the majority of volume is simple day trade straddles....meaning no short squeeze in the broader sense.