I could see this working very well for Southwest, though, for instance, as they already have everyone pre-line up not only by lettered zones, but also in groups of five within those zones (eg "B 15-20") at most every Southwest gate they service.
Instead of milling around the gate in the 15 minutes before boarding, they get everyone where they're supposed to go, and then funnel them through the door single file, in order. As the article references, though, it breaks down into a clogged jam-up of humanity trying to stuff their carry-ons into the compartment the moment you get to the plane.
I'm not sure this would work very well with Southwest because they don't assign seat numbers to passengers (at least in my experience). Most of the time, the people at the front of the group choose seats toward the front of the plane and hold up everyone else while they're stowing their bag.
Instead of milling around the gate in the 15 minutes before boarding, they get everyone where they're supposed to go, and then funnel them through the door single file, in order. As the article references, though, it breaks down into a clogged jam-up of humanity trying to stuff their carry-ons into the compartment the moment you get to the plane.