The author of the article makes a rather big assumption. That is, he assumes that shooting in such a way means the shooter is using the flat of the slide as an aiming plane.
I am not sure one can really make that assumption. Sure, it MIGHT work well (at least vertically), but it's going to take a split second to line up that slide with the target.
Furthermore, the author assumes that people doing this actually care where the bullets go and are not just trying to "spray and pray." Given the rather common results of drive-by shootings where a bunch of rounds are expended to little effect on the intended target, I would think it's more the latter than any unintentionally genius shooting system.
Myself, I'll stick with the sights. It might be a touch slower, but as the old saw goes, "You can't miss fast enough to win a gunfight."