Fringe theory that the only reason Columns (1990) even involves columns at all is because the programmers didn't feel like implementing piece rotation collision detection
On another note, I think it's very funny how Columns, Puyo Puyo, and other stuff like this game all avoid the big difficulty issue with Tetris (overhangs) by simply not allowing pieces to overhang ever.
*thinking to oneself in meditative contemplation* If the Columns magic gem was in Tetris, it would land on a row, and then all rows with an identical number of holes would be erased. *the corner of my lip imperceptibly twitches in satisfaction*