As the article correctly pointed out...and as you would have noted if you had read past the headline...such a system does not hold up when considering transaction costs.
Transaction costs are a serious drag on returns for any strategy that trades frequently, and they're often ignored by traders (and academics) thinking they've found the holy grail.
Your not paying attention:
On the other hand, buying and selling during the day has generally been a money-losing strategy — one that would have been far more painful if you had traded frequently, incurring steep costs, which would have compounded your losses.