People are just dumb sheep
While all this probably makes theoretic sense, I think in practice you could never get everybody lined up by rows, or if you did you would have to spend more time in the terminal getting everybody lined up in order than it takes to board the plane.
When they did the tests with people, they were working with volunteers with whom they probably did a detailed explanation first. These people weren't bored or not paying attention. They weren't giving in to the all too human urge to jump to the front of the line so they could get their carryon baggage stored. They probably didn't do any tests with young kids.
